Active material, nonaqueous electrolyte battery, battery pack and battery module

ABSTRACT

In general, according to one embodiment, there is provided an active material. The active material contains a composite oxide having an orthorhombic crystal structure. The composite oxide is represented by a general formula of Li 2+w Na 2−x M1 y Ti 6−z M2 z O 14+δ . In the general formula, the M1 is at least one selected from the group consisting of Cs and K; the M2 is at least one selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Fe, Co, Mn, and Al; and w is within a range of 0≦w≦4, x is within a range of 0&lt;x&lt;2, y is within a range of 0≦y&lt;2, z is within a range of 0&lt;z≦6, and δ is within a range of −0.5≦δ≦0.5.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe Japanese Patent Application No. 2015-050791, filed Mar. 13, 2015,and PCT Application No. PCT/JP2016/052708, filed Jan. 29, 2016, theentire contents of all of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to an active material fora battery, a nonaqueous electrolyte battery, a battery pack and abattery module.

BACKGROUND

Recently, a nonaqueous electrolyte battery such as a lithium ionsecondary battery has been actively researched and developed as a highenergy-density battery. The nonaqueous electrolyte battery is expectedto be used as a power source for hybrid vehicles, electric cars, anuninterruptible power supply for base stations for portable telephone,or the like. For this, the nonaqueous electrolyte battery is desired tohave a high energy density as well as to be excellent in otherperformances such as rapid charge-and-discharge performances andlong-term reliability. For example, a nonaqueous electrolyte batteryenabling rapid charge-and-discharge not only remarkably shortens acharging time but also makes it possible to improve performances relatedto motivity and to efficiently recover regenerative energy frommotivity, in a hybrid vehicle or the like.

In order to enable rapid charge-and-discharge, electrons and lithiumions must be able to migrate rapidly between the positive electrode andthe negative electrode. However, when a battery using a carbon-basednegative electrode is repeatedly subjected to rapidcharge-and-discharge, dendrite precipitation of metal lithium occurs onthe electrode, raising the fear as to heat generation and fires causedby internal short circuits.

In light of this, a battery using a metal composite oxide in place of acarbonaceous material in the negative electrode has been developed.Particularly, in a battery using titanium oxide as the negativeelectrode active material, rapid charge-and-discharge can be stablyperformed. Such a battery also has a longer life than those using acarbonaceous material.

However, titanium oxide has a higher potential based on metal lithiumthan the carbonaceous material. That is, titanium oxide is nobler.Furthermore, titanium oxide has a lower capacity per weight. Therefore,a battery using titanium oxide as the negative electrode active materialhas a problem that the energy density is lower. Particularly, when amaterial having a high potential based on metal lithium is used as anegative electrode material, a battery using the material has a lowervoltage than that of a conventional battery using a carbonaceousmaterial. Therefore, when the battery is used for systems requiring ahigh voltage such as an electric vehicle and a large-scale electricpower storage system, the battery has a problem that the battery seriesnumber is increased.

The potential of the electrode using titanium oxide is about 1.5 V basedon metal lithium and is higher (nobler) than that of the negativeelectrode using carbonaceous material. The potential of titanium oxideis due to the oxidation-reduction reaction between Ti³⁺ and Ti⁴⁺ whenlithium is electrochemically inserted and extracted, and is thereforelimited electrochemically. It is therefore conventionally difficult todrop the potential of the electrode to improve the energy density.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a charge-and-discharge curve of a composite oxideLi₂Na₂Ti₆O₁₄, and a charge-and-discharge curve of a composite oxideLi₂Na_(1.75)Ti_(5.75)Nb_(0.25)O₁₄;

FIG. 2 is a crystal structure view of Li₂Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄,which is one example of a composite oxide having symmetry of a spacegroup Fmmm;

FIG. 3 is a cross-sectional view of a nonaqueous electrolyte battery asan example according to a second embodiment;

FIG. 4 is an enlarged cross sectional view showing a portion A in FIG.3;

FIG. 5 is a partially cutaway perspective view schematically showing anonaqueous electrolyte battery as another example according to a secondembodiment;

FIG. 6 is an enlarged cross sectional view of a portion B in FIG. 5;

FIG. 7 is an exploded perspective view of a battery pack, which is oneexample according to a third embodiment;

FIG. 8 is a block diagram showing an electric circuit of the batterypack of FIG. 7;

FIG. 9 is a schematic perspective view of a battery module as an exampleaccording to a fourth embodiment.

FIG. 10 shows X-ray diffraction diagrams of products of Examples A-2,A-4, A-5, A-6 and A-9;

FIG. 11 shows initial charge-and-discharge curves obtained by anelectrochemical measurement of electrochemical measurement cells ofExamples A-4, A-5, A-6 and A-9 and an electrochemical measurement cellof Comparative Example A-1b;

FIG. 12 shows a discharge (Li extraction) curve ofLi₂Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄; and

FIG. 13 shows a charge-and-discharge curve of a nonaqueous electrolytebattery of Example E.

FIG. 14 shows charge-and-discharge curves of battery module of ExampleF-1 to F-4.

DETAILED DESCRIPTION

In general, according to one embodiment, there is provided an activematerial. The active material contains a composite oxide having anorthorhombic crystal structure. The composite oxide is represented by ageneral formula of Li_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O_(14+δ). In thegeneral formula, the M1 is at least one selected from the groupconsisting of Cs and K; the M2 is at least one selected from the groupconsisting of Zr, Sn, V, Nb, Ta, Mo, W, Fe, Co, Mn, and Al; and w iswithin a range of 0≦w≦4, x is within a range of 0<x<2, y is within arange of 0≦y<2, z is within a range of 0<z≦6, and δ is within a range of−0.5≦δ≦0.5.

The embodiments will be explained below with reference to the drawings.In this case, the structures common to all embodiments are representedby the same symbols and duplicated explanations will be omitted. Also,each drawing is a typical view for explaining the embodiments and forpromoting an understanding of the embodiments. Though there are partsdifferent from an actual device in shape, dimension and ratio, thesestructural designs may be properly changed taking the followingexplanations and known technologies into consideration.

First Embodiment

According to a first embodiment, an active material for a batterycontaining a composite oxide having an orthorhombic crystal structure isprovided. The composite oxide is represented by a general formula ofLi_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O_(14+δ). In the general formula,the M1 is at least one selected from the group consisting of Cs and K;the M2 is at least one selected from the group consisting of Zr, Sn, V,Nb, Ta, Mo, W, Fe, Co, Mn, and Al; and w is within a range of 0≦w≦4, xis within a range of 0<x<2, y is within a range of 0≦y<2, z is within arange of 0<z≦6, and δ is within a range of −0.5≦δ≦0.5.

The composite oxide contained in the active material for a batteryaccording to the first embodiment is a substituted composite oxide inwhich, in an orthorhombic crystal structure of a composite oxiderepresented by the general formula of Li_(2+w)Na₂Ti₆O_(14+δ), a part ofNa sites is substituted by a cation M1 and/or Na is removed from a partof the Na sites to form a vacancy, and at least a part of Ti sites issubstituted by a cation M2.

When an Na amount in the crystal structure of the composite oxide ischanged, an electrode potential behavior of the composite oxide based onthe oxidation-reduction potential of metal lithium is changed. Theactive material for a battery according to the first embodimentcontaining the composite oxide, which is represented by the generalformula Li_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O_(14+δ) wherein 0<x<2, canhave an average potential of lithium insertion of a range of 1.2 V (vs.Li/Li⁺) to 1.45 V (vs. Li/Li⁺) when an operating potential is within arange of 0.5 V to 3.0 V relative to the oxidation-reduction potential ofthe metal lithium. Thus, a nonaqueous electrolyte battery, using theactive material for a battery according to the first embodiment as anegative electrode active material can show a battery voltage higherthan that of, for example, a nonaqueous electrolyte battery using atitanium composite oxide which has an average potential of lithiuminsertion of 1.55 V (vs. Li/Li⁺) in a range of the same operatingpotential, as the negative electrode.

In a composite oxide which has a vacancy at a portion corresponding to apart of the Na sites of the composite oxide represented by the generalformula of Li_(2+w)Na₂Ti₆O_(14+δ), among the composite oxidesrepresented by the general formulaLi_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O_(14+δ), this vacancy can serve asa further site of insertion and extraction of Li ion. For this reason,in the composite oxide containing such a vacancy, Li ions can be moreeasily inserted and extracted than in the composite oxide represented bythe general formula of Li_(2+w)Na₂Ti₆O_(14+δ); as a result, a highercharge-and-discharge capacity can be realized.

In the active material according to the first embodiment, a correlationbetween a charging capacity and a battery voltage can be more easilycomprehended than in the composite oxide represented by the generalformula of Li_(2+w)Na₂Ti₆O_(14+δ), in a potential range of 1.0 V (vs.Li/Li⁺) to 1.45 V (vs. Li/Li⁺). Referring FIG. 1, the reason why thecorrelation between the charging capacity and the battery voltage can bemore easily comprehended in the active material for a battery accordingto the first embodiment is explained below.

FIG. 1 shows a charge-and-discharge curve (a broken line) of a compositeoxide Li₂Na₂Ti₆O₁₄, and a charge-and-discharge curve (a solid line) of acomposite oxide Li₂Na_(1.75)Ti_(5.75)Nb_(0.25)O₁₄. The composite oxideLi₂Na_(1.75)Ti_(5.75)Nb_(0.25)O₁₄, whose potential change is shown bythe solid line, has an orthorhombic crystal structure, and is acomposite oxide which can be contained in the active material for abattery according to the first embodiment. On the other hand, thecomposite oxide Li₂Na₂Ti₆O₁₄, whose potential change is shown by thebroken line, is a composite oxide represented by the general formula ofLi_(2+w)Na₂Ti₆O_(14+δ), and having an orthorhombic crystal structure. Itcan also be said that the composite oxideLi₂Na_(1.75)Ti_(5.75)Nb_(0.25)O₁₄ is a substituted oxide in which Na isremoved from a part of the Na sites of the crystal structure of thecomposite oxide Li₂Na₂Ti₆O₁₄ to form a vacancy, and a part of the Tisites thereof is substituted by Nb.

As shown by the a broken line in FIG. 1, each of the charge curve andthe discharge curve of the composite oxide Li₂Na₂Ti₆O₁₄ contains a flatportion, in which a variation in the potential accompanied with a changein the capacity is small, as majority excluding an initial stage and alast stage of each of the charge and discharge. For example, it isfound, from a charge curve in an Li insertion direction, when thecomposite oxide Li₂Na₂Ti₆O₁₄ is subjected to charge from a potential of1.35 V (vs. Li/Li⁺) to a potential of 1.20 V (vs. Li/Li⁺), about 80mAh/g is charged in this small difference in potential of 0.15 V. Thischarge capacity corresponds to about 90% of the total charge capacity ofthe composite oxide Li₂Na₂Ti₆O₁₄. Similarly, it is found, from adischarge curve in an Li extraction direction, when the composite oxideLi₂Na₂Ti₆O₁₄ is subjected to discharge from a potential of 1.20 V (vs.Li/Li⁺) to a potential of 1.35 V (vs. Li/Li⁺), about 90% of the totaldischarge capacity is discharged in this small difference in potentialof 0.15 V. Thus, the charge curve and the discharge curve of thecomposite oxide Li₂Na₂Ti₆O₁₄ hardly show change in the potentialaccompanied with the changes of the charged capacity and the dischargedcapacity. That is, each of the charge and discharge curves of thecomposite oxide Li₂Na₂Ti₆O₁₄ contains the region in which the potentialgradient is small as majority. In a nonaqueous electrolyte batteryproduced using the composite oxide having such a potential change in anegative electrode, it is difficult to comprehend the correlationbetween the charging capacity and the battery voltage, and to controlSOC during the charge and discharge.

On the other hand, as shown by a solid line in FIG. 1, it is found thateach of a charge curve and a discharge curve of the composite oxideLi₂Na_(1.75)Ti_(5.75)Nb_(0.25)O₁₄ has, as majority excluding the initialstage and the last stage of the charge and the discharge, a portion inwhich a variation in the potential accompanied with a change in thecapacity is large. Specifically, it is found from the charge curve inthe Li insertion direction that when the charge is started from apotential of 1.50 V (vs. Li/Li⁺) and reaches 90% of the total capacity,the potential of the composite oxide Li₂Na_(1.75)Ti_(5.75)Nb_(0.25)O₁₄becomes about 1.15 V (vs. Li/Li⁺); in other words, the composite oxideLi₂Na_(1.75)Ti_(5.75)Nb_(0.25)O₁₄ exhibits a variation in the potentialof about 0.35 V during the charge. Similarly, it is found from thedischarge curve in the Li extraction direction that when the dischargeis started from a potential of 1.15 V (vs. Li/Li⁺) and reaches 90% ofthe total capacity, the capacity of the composite oxideLi₂Na_(1.75)Ti_(5.75)Nb_(0.25)O₁₄ becomes about 1.50 V (vs. Li/Li⁺), andthere is a variation in the potential of about 0.35 V during thedischarge. Thus, each of the charge and discharge curves of thecomposite oxide Li₂Na_(1.75)Ti_(5.75)Nb_(0.25)O₁₄ contains, as majority,a portion in which a variation in the potential accompanied with achange in the capacity which is larger than that in the potential flatportion contained in the charge-and-discharge curve of the compositeoxide Li₂Na₂Ti₆O₁₄, i.e., a portion having a larger gradient than thepotential flat portion.

In addition, as shown by the solid line in FIG. 1, thecharge-and-discharge curve of the composite oxideLi₂Na_(1.75)Ti_(5.75)Nb_(0.25)O₁₄ exhibits, excluding the initial stageand the last stage thereof, a continuous potential change which does notcontain a potential step in which the potential steeply changes duringthe charge-and-discharge.

It is easy to comprehend the correlation between thecharged-and-discharged capacity and the battery voltage for thenonaqueous electrolyte battery produced using the composite oxideexhibiting the potential change described above in the negativeelectrode, and thus the SOC of the battery can be easily managed.

As apparent from the charge-and-discharge curve shown in FIG. 1, thecomposite oxide Li₂Na₂Ti₆O₁₄ exhibits a charge-and-discharge capacity ofabout 90 mAh/g. On the other hand, the composite oxideLi₂Na_(1.75)Ti_(5.75)Nb_(0.25)O₁₄ exhibits a charge-and-dischargecapacity of 115.9 mAh/g, and can exhibit a charge-and-discharge capacitywhich is higher than that of the composite oxide Li₂Na₂Ti₆O₁₄.

The composite oxide contained in the active material for a batteryaccording to the first embodiment can exhibit a continuous potentialchange which does not contain a potential steps within the potentialrange of 1.0 V to 1.45 V (vs. Li/Li⁺) because it can have uniforminsertion sites of lithium. The reason for this will be described below.

The composite oxide, which can be contained in the active material for abattery according to the first embodiment, is represented by the generalformula of Li_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O_(14+δ). In thiscomposite oxide, Li exists as a monovalent cation. M1 is at least onemonovalent cation selected from the group consisting of Cs and K. M1 maybe one of Cs and K, or both of Cs and K. M2 is at least one selectedfrom the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Fe, Co, Mn andAl. M2 may be one selected from the group consisting of Zr, Sn, V, Nb,Ta, Mo, W, Fe, Co, Mn and Al, or be two or more selected from the groupconsisting of Zr, Sn, V, Nb, Ta, Mo, W, Fe, Co, Mn and Al. Here, each ofFe, Co, Mn and Al is a trivalent cation. Each of Zr and Sn is atetravalent cation. Each of V, Nb and Ta is a pentavalent cation. Eachof Mo and W is a hexavalent cation. Here, the valence of each cationdescribed above are a valence of each cation when w is 0 in the abovegeneral formula, i.e., in a discharge state.

In this composite oxide, the total valence of the cations coincides withthe total valence of oxide ions which are anions, and thus the chargeneutrality can be maintained. Specifically, in this composite oxide, thetotal valence of the lithium ions is 2+w. The total valence of thesodium ions is 2−x. The total valence of the M1 is y. The total valenceof Ti is 4×(6−z). The total valence of the M2 is, if one mole of thecomposite oxide contains z₃ mole of the trivalent cation M2₃, z₄ mole ofthe tetravalent cation M2₄, z₅ mole of the pentavalent cation M2₅, andz₆ mole of the hexavalent cation M2₆, (z₃×3)+(z₄×4)+(z₅×5)+(z₆×6),wherein z₃+z₄+z₅+z₆=z. The total valence of these cations coincides withthe total valence of oxide ions which are anions: (−2)×(14+δ). Here, thesubscript of the oxide ion δ can have a value within a range of −0.5 to0.5, and thus the same effects can be obtained even if the total valenceof the cations described above varies within a range of ±1 to −28valences, which is the total valence of the oxide ions. If the δ isbeyond the range of −0.5≦δ≦0.5, there is a possibility of theoxidation-reduction state of the cations deviating from a stable state,or a lattice defects such as an oxygen deficiency occuring, thusundesirably resulting in reduced battery performance.

Here, assuming that the cations forming the composite oxide are in astable oxidation state, and oxide ions exist in a proper quantity, δ=0,and thus the total valence of the oxide ions is −2×14=−28. In this case,the state in which the total valence of the cations coincides with thetotal valence of the oxide ions is represented by the following formula(1):

(2+w)+(2−x)+y+{4×(6−z)}+{(z ₃×3)+(z ₄×4)+(z ₅×5)+(z ₆×6)}−28=0  (1)

The formula (1) can be organized into the following formula (2):

w−x+y−4z+(3z ₃+4z ₄+5z ₅+6z ₆)=0  (2)

The charge neutrality in the crystal structure of the composite oxidecan be maintained by satisfying the conditions of the formula (2). Thecomposite oxide Li_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O_(14+δ) whosecharge neutrality is maintained is a substituted oxide in which a partof the Ti sites is properly substituted by the cation M2 in the crystalstructure of the composite oxide represented by the general formula ofLi_(2+w)Na₂Ti₆O_(14+δ). In addition, the composite oxideLi_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O_(14+δ) in which charge neutralityis maintained and y is greater than 0 is a substituted oxide in which apart of the Na sites is properly substituted by the cation M1 in thecrystal structure of the composite oxide represented by the generalformula of Li_(2+w)Na₂Ti₆O_(14+δ). In addition, in the composite oxideLi_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O_(14+δ) whose charge neutrality ismaintained, a part corresponding to a part of the Na sites in thecrystal structure of the composite oxide represented by the generalformula of Li_(2+w)Na₂Ti₆O_(14+δ) can stably exist as a vacancy in thecrystal structure. By containing the substituted oxide in which thecation M2 is properly substituted in the crystal structure of thecomposite oxide represented by the general formula ofLi_(2+w)Na₂Ti₆O_(14+δ) and which contains the properly substitutedcation M1 and/or the vacancy which can stably exist in the crystalstructure of the composite oxide represented by the general formula ofLi_(2+w)Na₂Ti₆O_(14+δ), as described above, the active material for abattery according to the first embodiment can make a coordinationenvironment of the oxide ions to void sites where the lithium ions areinserted uniform. This is a reason why the composite oxide, which can becontained in the active material for a battery according to the firstembodiment, can show a continuous potential change within a potentialrange of 1.0 V to 1.45 V (vs. Li/Li⁺). On the other hand, a compositeoxide in which the uniformity of the coordination environment of theoxide ions to the void sites is low exhibits a potential step in thecharge-and-discharge curve, i.e., a steep change in the potential.

In addition, by containing the substituted oxide in which the cation M2is properly substituted in the crystal structure of the composite oxiderepresented by the general formula of Li_(2+w)Na₂Ti₆O_(14+δ) and whichcontains the properly substituted cation M1 and/or the vacancy which canstably exist in the crystal structure of the composite oxide representedby the general formula of Li_(2+w)Na₂Ti₆O_(14+δ), the active materialfor a battery according to the first embodiment can provide a nonaqueouselectrolyte battery capable of exhibiting the high reversible capacityin the charge and discharge and the excellent life performance. Inparticular, the substituted oxide in which a part of the Na sites in thecomposite oxide Li_(2+w)Na₂Ti₆O_(14+δ) are substituted by the vacancywhich can stably exist can realize the higher reversible capacity,because electrical charge repulsion of sites, which can serve as hostfor Li ions, is reduced.

Consequently, the active material for a battery according to the firstembodiment can realize a nonaqueous electrolyte battery which canexhibit high energy density and high battery voltage, can exhibit anexcellent life performance, and can provide easy voltage management.

The subscript w in the general formula ofLi_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O_(14+δ) for the composite oxide canvary within a range of 0≦w≦4 depending on the state-of-charge of thecomposite oxide. For example, according to a production method describedbelow, a composite oxide in which the subscript w is 0 in the generalformula described above can be manufactured. When the composite oxide inwhich the subscript w is 0 is incorporated in a nonaqueous electrolytebattery as the negative electrode active material, and the resultingnonaqueous electrolyte battery is charged, the value of w+2 is elevatedto a value within a range of more than 2 and 6 or less. Alternatively, acomposite oxide can also be synthesized in a raw material compositionratio set so that an Li amount in the formula, w+2, is within a range ofmore than 2 and 6 or less before the initial charge, for example, by theprocess described below. The active material for a battery containingthe composite oxide having an Li amount, w+2, within a range of morethan 2 and 6 or less before the initial charge can suppress the trappingof lithium ions in its structure during the initialcharge-and-discharge, and as a result, the initial charge-and-dischargeefficiency can be improved.

The subscript x in the general formula ofLi_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O_(14+δ) for the composite oxideindicates an Na amount in the crystal structure in this composite oxide.The active material for a battery according to the first embodiment cancontrol an average operating potential of an electrode containing theactive material for a battery within a range of 1.2 V (vs. Li/Li⁺) to1.5 V (vs. Li/Li⁺) to the oxidation-reduction potential of the metallithium by changing the Na amount in the crystal structure, i.e., thevalue of the subscript x, whereby the operating potential of the batterycan be easily designed. From a different aspect, the subscript x is anindex showing a ratio of a part which is substituted by the cation M1 orthe vacancy in the substituted composite oxide, among the sitescorresponding to the Na sites in the composite oxideLi_(2+w)Na₂Ti₆O_(14+δ). The subscript x is within a range of 0<x<2,preferably 0.1≦x≦0.9, more preferably 0.25≦x≦0.75.

The subscript y in the general formula ofLi_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O_(14+δ) indicates an amount ofcation M1 contained in the crystal structure of the composite oxiderepresented by this general formula. In addition, the cation M1 is onewith which a part of the Na sites in the composite oxideLi_(2+w)Na₂Ti₆O_(14+δ) is substituted. Accordingly, the combination ofthe subscript x and the subscript y is an index showing a ratio of apart which is substituted by the cation M1 in the substituted compositeoxide, among the sites corresponding to the Na sites in the compositeoxide Li_(2+w)Na₂Ti₆O_(14+δ). The value of the subscript y is,accordingly, a value equal to or less than the value of the subscript x.

The subscript y is within a range of 0≦y<2. Therefore, the value of thesubscript y may be 0. That is, the composite oxide, represented by thegeneral formula of Li_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O_(14+δ), maycontain no cation M1. When the value of the subscript y is 0, thecomposite oxide, contained in the active material for a batteryaccording to the first embodiment, is represented by the general formulaof Li_(2+w)Na_(2−x)Ti_(6−z)M2_(z)O_(14+δ). In this composite oxide, apart corresponding to a part of the Na sites in the composite oxideLi_(2+w)Na₂Ti₆O_(14+δ), i.e., a part indicated by the subscript x isvacancy.

When Na ion are removed from a part of the Na sites in the compositeoxide Li_(2+w)Na₂Ti₆O_(14+δ) to form vacancy, the total valence of thecations in the composite oxide is reduced. Specifically, when x moles ofNa ions are removed from one mole of the composite oxideLi_(2+w)Na₂Ti₆O_(14+δ) to form x moles of vacancies, the total valenceof the cations in this composite oxide is reduced by x. In such a case,the charge neutrality can be maintained, for example, by inserting Liions into the formed vacancies or by substituting a part of Ti sites inthe composite oxide Li_(2+w)Na₂Ti₆O_(14+δ) by the pentavalent M2₅ or thehexavalent M2₆ as the cation M2, so as to compensate the reducedvalences x. Such a substitution can reduce Na ions, which impedeslithium ion conduction, and vacancies, which are host sites of Li ions,can be increased, while the crystal structure of the composite oxideLi_(2+w)Na₂Ti₆O_(14+δ) is maintained. Thus, the substituted compositeoxide capable of realizing the improved charge-and-discharge capacitycan be obtained.

The subscript y is preferably within a range of 0≦y≦1, more preferably0.

The subscript z in the general formula ofLi_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O_(14+δ) for the composite oxideindicates an amount of the cation M2 contained in the crystal structureof the composite oxide represented by this general formula. In addition,the cation M2 is one with which a part of the Ti sites in the compositeoxide Li_(2+w)Na₂Ti₆O_(14+δ) is substituted. Therefore, the subscript zis an index showing a ratio of a part which is substituted by the cationM2 in the substituted composite oxide, among the sites corresponding tothe Ti sites in the composite oxide Li_(2+w)Na₂Ti₆O_(14+δ). Thesubscript z is within a range of 0<z≦6, preferably 0.1≦z≦0.9, morepreferably 0.25≦z≦0.75.

The subscript δ in the general formula ofLi_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O_(14+δ) for the composite oxide mayvary within a range of −0.5≦δ≦0.5 depending on the oxygen deficiency ofthe composite oxide represented by this general formula or the amount ofoxygen inevitably incorporated during the production process of theactive material for a battery.

Although each of the subscripts w, x, y, z and δ can be a value withinthe specific range as described above, in the composite oxiderepresented by the general formula ofLi_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O_(14+δ), the total valence of thecations is equal to the total valence of the anions, as described above.

In an X-ray diffraction diagram for the composite oxide represented bythe general formula of Li_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O_(14+δ),obtained by a powder X-ray diffraction using Cu—Kα rays, it ispreferable that an intensity ratio I_(L)/I_(H) is within a range of2.25≦I_(L)/I_(H)≦3.50, wherein I_(L) is an intensity of a strongestdiffraction peak appearing in a range of 17°≦2θ≦18.5°, and I_(H) is anintensity of a strongest diffraction peak appearing in a range of18.5°<2θ≦19.5°.

A composite oxide according to another example of the preferable aspectsin which the intensity ratio I_(L)/I_(H) is within a range of2.25≦I_(L)/I_(H)≦3.5 in an X-ray diffraction diagram of a compositeoxide, obtained according to a powder X-ray diffraction, is a compositeoxide having an orthorhombic crystal structure belonging to a spacegroup Fmmm. In such a composite oxide, in the X-ray diffraction diagramof the composite oxide obtained by the powder X-ray diffraction usingCu—Kα rays, an intensity ratio is within a range of2.25≦I_(L1)/I_(H1)≦3.5, wherein I_(L1) is an intensity of a diffractionpeak corresponding to a (111) plane, and I_(H1) is an intensity of adiffraction peak corresponding to a (202) plane.

FIG. 2 is a crystal structure view of Li₂Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄which is one example of the composite oxide having the symmetry of thespace group Fmmm.

In the crystal structure shown in FIG. 2, the smallest spheres 100indicate positions of oxide ions.

In the crystal structure shown in FIG. 2, a region A shows a void sitecontaining a channel in which the lithium ion can three-dimensionallymove in the crystal structure, and the region A can insert and extractthe lithium ions. A region B has a polyhedral structure of oxide havinga center of Ti or Nb, serving as the backbone of the crystal structure.On the other hand, a region C is a site in which lithium ions which canbe inserted and extracted exist. A region D is a site in which Na andLi, which functions as a backbone for stabilizing the crystal structure,or in which a vacancy exist.

In the X-ray diffraction diagram of the composite oxide of this examplemeasured according to the powder X-ray diffraction using Cu—Kα rays, anintensity ratio I_(L1)/I_(H1) is within a range of2.25≦I_(L1)/I_(H1)≦3.5. Here, I_(L1) is an intensity of a diffractionpeak corresponding to a (111) plane, appearing in a range of17.8°≦2θ≦18.5°, and I_(H1) is an intensity of a diffraction peakcorresponding to a (202) plane, appearing in a range of 18.5°≦2θ≦19.5°.

The composite oxide of this example can have crystallites grown in adesired direction for insertion and extraction of lithium ions.Furthermore, the composite oxide of this example can suppress theinsertion of lithium ions into void sites the oxide-ions coordinationenvironments of which are different to each other. Such an insertion oflithium ions is a cause for creating a potential step in thecharge-and-discharge curve. In the active material containing thecomposite oxide of this example, accordingly, the appearance of thepotential step can be suppressed on the charge-and-discharge curve, andthe reversibility of the lithium ions is improved during thecharge-and-discharge. Therefore, the effective capacity can beincreased, and the life performance of the nonaqueous electrolytebattery can be improved, which is preferable.

Even if the active material for a battery according to the firstembodiment contains a composite oxide having a crystal structure inwhich a crystal phase having a symmetry other than the Fmmm symmetry ismixed, or a composite oxide having a crystal structure similar to theFmmm symmetry, the same effects as those obtained in the active materialfor a battery containing the composite oxide having the symmetry of thespace group Fmmm can be obtained. Examples of the symmetry similar tothe Fmmm symmetry may include, specifically, Cmca, F222, Pmcm, Pmma,Cmma, and the like. The type of symmetry of a space group may be one ormore than one. In the composite oxide having the crystal structurehaving each of the symmetries described above, regardless of the crystalplane indices, an intensity ratio I_(L)/I_(H) is preferably within arange of 2.25≦I_(L)/I_(H)≦3.5, wherein I_(L) is an intensity of astrongest diffraction peak appearing in a range of 17°≦2θ≦18.5°, andI_(H) is an intensity of a strongest diffraction peak appearing in arange of 18.5°<2θ≦19.5°. In such a case, not only is thecharge-and-discharge curve smooth but also the reversibility of thelithium ion is improved in the charge-and-discharge, whereby theeffective capacity is increased, and the life performance of thenonaqueous electrolyte battery can be improved.

In one preferable aspect, the active material for a battery according tothe first embodiment contains the composite oxide represented by thegeneral formula of Li_(2+w)Na_(2−x)Ti_(6−z)M2_(z)O_(14+δ). In theformula, M2 is at least one selected from the group consisting of Zr,Sn, V, Nb, Ta, Mo, W, Fe, Co, Mn, and Al; w is within a range of 0≦w≦4;x is within a range of 0<x<2; z is within a range of 0<z≦6; and δ iswithin a range of −0.5≦δ≦0.5.

In the orthorhombic crystal structure of the composite oxide representedby the general formula of Li_(2+w)Na₂Ti₆O₁₄, a part of the Na sites isreduced and vacancy sites, which serve as hosts for the Li ions, can beformed, whereby the energy density per unit weight or unit volume can beincreased while a lattice volume capable of easily inserting andextracting the lithium ions is maintained. In addition, when the Naamount is changed, the average operating potential of the electrode canbe changed, whereby it is easy to design the voltage of the battery.

Furthermore, a more preferable aspect among these aspects is a compositeoxide in which the cation M2 is Nb. In the more preferable aspect,accordingly, the composite oxide contained in the active material for abattery according to the first embodiment is represented by the generalformula of Li_(2+w)Na_(2−x)Ti_(6−z)Nb_(z)O_(14+δ). Nb can be subjectedto a divalent reduction from the pentavalent Nb to the trivalent Nb, andthus at least a part of the Ti ions, which can be subjected to amonovalent reduction from the tetravalent Ti to the trivalent Ti, aresubstituted by Nb, and, on the other hand, vacancy sites are formed onthe Na sites, whereby the lithium insertion amount of the compositeoxide can be increased. When Nb is contained in the crystal structure, apotential based on the oxidation-reduction potential of the metallithium during the insertion of Li is continuously changed in a widerange of 1.5 V to 1.0 V. When at least a part of the Ti ions issubstituted by Nb, therefore, not only is the charge-and-dischargecapacity increased but also a part where the variation in the potentialaccompanied with a change in the capacity is larger can be contained inthe charge-and-discharge curve. The composite oxide, which can exhibitsuch a charge-and-discharge curve, can easily correlate the charge anddischarge potential with the state-of-charge (SOC), and thestate-of-charge of the battery can be easily managed.

In another preferable aspect, a composite oxide contained in the activematerial for a battery according to the first embodiment contains two ormore elements which have different valences from each other at sitescorresponding to the Ti sites in the composite oxideLi_(2+w)Na₂Ti₆O_(14+δ). Such a composite oxide has a larger potentialgradient during the charge-and-discharge, and therefore is preferable.The reason why the potential gradient is larger is, for example, thatthere are two or more elements having electrical correlations with theoxide ion different from each other at sites corresponding to titaniumsites in the crystal structure of the composite oxideLi_(2+w)Na₂Ti₆O_(14+δ), and thus multiple sites, which have a differencefrom each other in electrical correlation with the Li ion and with theoxide ion respectively, are generated at these sites. More specifically,an element having a higher valence contained in these sites has atendency to take more of an electron cloud of the oxide ion and, on theother hand, an element having a lower valence has a tendency in whichthe correlation between the oxide ion and the electron cloud is weak.Therefore, a difference occurs in an electrical state of the oxide ionnear to the lithium host site, and as a result, the electricalcorrelation which is provided to the lithium ion from the lithium hostsite becomes different. Consequently, the variation in the potential dueto the insertion and extraction of the lithium ion increases.

The composite oxide contained in the active material for a batteryaccording to the first embodiment may be in the state of, for example, aparticle. An average particle size of the composite oxide contained inthe active material for a battery according to the first embodiment isnot particularly limited, and may be varied depending on the desiredbattery characteristic.

It is preferable that the active material for a battery according to thefirst embodiment contains the composite oxide particles described above,and a conductive substance such as carbon with which the surface of theparticles is covered. The active material for a battery according tosuch a preferable aspect can exhibit an improved quickcharge-and-discharge performance. In the composite oxide describedabove, the lithium is inserted and extracted via a homogeneous solidstate reaction, and thus the composite oxide has a nature in which thehigher the lithium insertion amount, the higher the electricalconductivity. In such a composite oxide, the electrical conductivity isrelatively reduced in a region where the lithium insertion amount issmall. When the surface of the composite oxide particle is previouslycoated with a conductive substance such as carbon, accordingly, the highquick-charge-and-discharge performance can be obtained regardless of thelithium insertion amount.

Alternatively, the same effects as above can be obtained by coating thesurface of the composite oxide particles with lithium titanate, whichexpresses electrical conductivity with the lithium insertion, instead ofthe conductive substance such as carbon. In addition, since lithiumtitanate with which the surface of the composite oxide particles iscovered exhibit an insulation property by the extraction of lithium whenthe battery is internally short-circuited, the lithium titanate canexhibit excellent safety.

<BET Specific Surface Area>

The BET specific surface area of the composite oxide contained in theactive material for a battery according to the first embodiment is notparticularly limited, and is preferably 5 m²/g or more and less than 200m²/g. The BET specific surface area is more preferably 5 to 30 m²/g.

When the BET specific surface area is 5 m²/g or more, the contact areawith the electrolytic solution can be secured. Thus, good discharge rateperformances can be easily obtained and also, a charge time can beshortened. On the other hand, when the BET specific surface area is lessthan 200 m²/g, reactivity with the electrolytic solution can beprevented from being too high and therefore, the life performance can beimproved. When the BET specific surface area is 30 m²/g or less, sidereactions with the electrolytic solution can be suppressed, and therebylonger life can be further expected. And, in this case, a coatability ofa slurry containing the active material for a battery in the productionof an electrode, which will be described later, can be improved.

Here, as the measurement of the specific surface area, a method is used,the method including allowing molecules of which an occupied area inadsorption is known to be adsorbed onto the surface of powder particlesat the temperature of liquid nitrogen and determining the specificsurface area of the sample from the amount of adsorbed molecules. Themost frequently used method is a BET method based on the lowtemperature/low humidity physical adsorption of an inert gas. Thismethod is based on the best-known theory of the method of calculatingthe specific surface area in which the Langmuir theory as a monolayeradsorption theory is extended to multilayer adsorption. The specificsurface area determined by the above method is referred to as “BETspecific surface area”.

<Production Method>

The active material for a battery according to the first embodiment canbe synthesized, for example, by a solid phase reaction as describedbelow. First, raw materials, such as oxide, compound, and a salt, aremixed in a proper stoichiometric ratio to obtain a mixture. The saltsare preferably salts capable of decomposing at a comparatively lowtemperature to generate an oxide, such as carbonates and nitrates. Next,the obtained mixture is ground and mixed as uniformly as possible.Subsequently, the resulting mixture is calcinated. The calcination isperformed at a temperature range of 600° C. to 850° C. in an airatmosphere for a total of 1 to 3 hours. Next, the firing temperature isincreased and the main-sintering is performed at 900° C. to 1500° C. inthe atmosphere. At that time, the lithium, which is a light element, maybe vaporized by firing it at a temperature of 900° C. or higher. In sucha case, a vaporized amount of lithium in the firing conditions ischecked, and the vaporized amount checked up is compensated for byproviding a raw material containing lithium in an excess amount toobtain a sample having a proper composition. Furthermore, it is morepreferable to prevent a lattice defect due to oxygen deficiency or thelike. For example, the raw material powder is subjected to pressuremolding to pellets or rods before the main-sintering to decrease an areabrought into contact with the air atmosphere and to increase the contactsurface between particles. When a material in this state is sintering,the generation of the lattice defect can be suppressed. It is alsoeffective to prevent the vaporization of the light elements by attachinga lid to a nagger for sintering. In a case of industrial massproduction, it is preferable that when the raw material powder issintering, the sintering is performed under a high oxygen partialpressure such as an oxygen atmosphere, or after the usual air-atmospheresintering, a heat treatment (annealing) is performed at a temperaturerange of 400° C. to 1000° C. to restore the oxygen deficiency. If thegeneration of the lattice defect is not suppressed, the crystallinitymay possibly be reduced.

When the composite oxide obtained by the synthesis above has a symmetrybelonging to the space group Fmmm, the intensity ratio is within a rangeof 2.25≦I_(L1)/I_(H1)≦3.5 in the X-ray diffraction diagram obtainedaccording to the powder X-ray diffraction using Cu—Kα rays. Theintensitiy I_(L1) is an intensity of a diffraction peak corresponding toa (111) plane, appearing in a range of 17.8°≦2θ≦18.5°, and the intensityI_(H1) is an intensity of a diffraction peak corresponding to a (202)plane, appearing in a range of 18.5°<2θ≦19.5°.

When the synthesis is performed as described above, for example, thecomposite oxide represented by the above general formula wherein thesubscript w is 0 can be produced, as explained above. When the compositeoxide wherein the subscript w is 0 is incorporated into the nonaqueouselectrolyte battery as the negative electrode active material, and theresulting nonaqueous electrolyte battery is charged, a state in whichthe Li amount w+2 in the formula is increased to a range of more than 2and 6 or less is made. Alternatively, when a lithium source such aslithium carbonate is used as a raw material, and the composite oxide issynthesized in a raw material composition ratio so that the value of wis within a range of more than 0 and 4 or less, the composite oxide in astate in which the value of w+2 is within a range of more than 2 and 6or less can also be synthesized. In addition, the composite oxide in astate in which the value of w+2 is within a range of more than 2 and 6or less can also be obtained by, after the composite oxide issynthesized, immersing the composite oxide into the aqueous lithiumhydroxide solution.

Next, a method for obtaining the X-ray diffraction diagram of thecomposite oxide according to the powder X-ray diffraction, and a methodfor confirming the composition of the composite oxide will be described.

When an active material to be measured is contained in an electrodematerial of a nonaqueous electrolyte battery, a pre-treatment isperformed as described below.

First, a state in which lithium ions are completely removed from thecrystals of the active material is made. When the active material to bemeasured is contained in the negative electrode, the battery is made tobe in a completely discharged state. However, there are remaininglithium ions even if in the discharged state, but the existence thereofdoes not greatly affect the measurement results of the powder X-raydiffraction described below.

Next, the battery is disassembled in a glove box filled with argon totake out an electrode. The taken-out electrode is washed with anappropriate solvent and dried under a reduced pressure. For example,ethyl methyl carbonate may be used. After washing and drying, whether ornot there are white precipitates such as a lithium salt on the surfaceis confirmed.

When the powder X-ray diffraction measurement is performed, the washedelectrode is cut into a size having the same area as that of a holder inthe powder X-ray diffraction apparatus, for used as a measurementsample.

When a composition analysis is performed, the active material is takenout from the washed electrode, and the taken-out active material isanalyzed, as described later.

<Method for Obtaining X-Ray Diffraction Diagram of Composite OxideAccording to Powder X-Ray Diffraction>

The powder X-ray diffraction measurement of the active material isperformed as follows:

First, the target sample is ground until an average particle sizereaches about 5 μm. Even if the original average particle size is lessthan 5 μm, it is preferable that the sample is subjected to a grindingtreatment with a mortar for grinding aggregates. The average particlesize can be obtained by laser diffraction. The ground sample is filledin a holder part having a depth of 0.5 mm, formed on a glass sampleplate. A glass sample plate manufactured by Rigaku Corporation is usedas the glass sample plate. At this time, much care is necessary to fillthe holder part fully with the sample. Special care should be taken toavoid cracking and formation of voids caused by insufficient filling ofthe sample. Then, another glass plate is used to smooth the surface ofthe sample by sufficiently pressing the glass plate against the sample.In this case, much care should be taken to avoid too much or too littleamount of the sample to be filled, so as to prevent any rises and dentsin the basic plane of the glass holder. Then, the glass plate filledwith the sample is set in a powder X-ray diffractometer. And then, adiffraction pattern [XRD (X-ray diffraction) pattern] is obtained byusing Cu—Kα rays.

In the case where an orientation in which crystal planes are arranged ina specific direction according to the shapes of particles is observedfrom the results of the Rietveld analysis, there is the possibility ofdeviation of peak position and variation in an intensity ratio,depending on the way of filling the sample when the glass plate isfilled with the sample. Such a sample having high orientation ismeasured using a capillary (cylindrical glass narrow tube).Specifically, the sample is inserted into the capillary, which is thenmounted on a rotary sample table to measure while being rotated. Such ameasuring method can provide the result of reducing the influence oforientation.

As an apparatus for powder X-ray diffraction measurement, SmartLabmanufactured by Rigaku is used. Measurement is performed under thefollowing condition: Cu target; 45 kV, 200 mA; soller slit: 5 degrees inboth incident light and received light; step width: 0.02 deg; scanspeed: 20 deg/min; semiconductor detector: D/teX Ultra 250; sample plateholder: flat glass sample plate holder (0.5 mm in thickness);measurement range: 5°≦2θ≦90°. When another apparatus is used,measurement using a standard Si powder for powder X-ray diffraction isperformed under conditions where a peak intensity and a peak topposition correspond to those by obtained using the above apparatus so asto obtain measurement results equivalent to those described above.

The X-ray diffraction (XRD) pattern obtained herein must be applicableto Rietveld analysis. In order to collect the data for Rietveldanalysis, the measurement time or X-ray intensity is appropriatelyadjusted in such a manner that the step width is made ⅓ to ⅕ of theminimum half width of the diffraction peaks, and the intensity at thepeak position of strongest reflected intensity is 5,000 cps or more.

The XRD pattern obtained as described above is analyzed by the Rietveldmethod. In the Rietveld method, the diffraction pattern is calculatedfrom the crystal structure model which has been previously estimated.The parameters of the crystal structure (lattice constant, atomiccoordinate, and crystal site occupancy ratio or the like) can beprecisely analyzed by fitting all the calculated values and measurementvalues. Thereby, the characteristics of the crystal structure of thesynthesized composite oxide can be determined. The site occupancy ratiog of constitutional elements in each of the sites can be determined. Afitting parameter S is used as the scale for estimating the degree ofagreement between the measured reflection patterns and the calculatedpatterns in the Rietveld analysis. The S value must be less than 1.8 inthe analysis. When determining the occupancies in each of the sites, thestandard deviation σ_(j) must be taken into consideration. The fittingparameter S and standard deviation σ_(j) defined herein are estimatedusing the formula described in “Funmatsu X sen Kaisetsu no Jissai(Reality of Powder X-Ray Analysis”, X-Ray Analysis InvestigationConversazione, The Japan Society for Analytical Chemistry, written andedited by Izumi Nakai and Fujio Izumi (Asakura Publishing Co., Ltd.).

By the above method, information about the crystal structure of theactive material to be measured can be obtained. For example, when theactive material according to the first embodiment is measured asdescribed above, the active material to be measured is found to have acomposite oxide having an orthorhombic structure. The symmetry of thecrystal structure to be measured, such as space group Fmmm, can beexamined, for example, by measuring as described above. Furthermore, theexistence or non-existence of a vacancy and the amount of vacancies canbe determined by more precisely refining the occupancies ofconstitutional elements in each of the sites. For example, to determinethe existence or non-existence of a vacancy in the Na sites of a crystalrepresented by the general formula ofLi_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O_(14+δ), Rietveld analysis may beperformed while changing the site occupancy ratio of Na. First, assumethat the fitting parameter in Rietveld analysis performed at theoccupancy ratio g of 1.0, that is, 100%, is S₁₀₀. Then, assume that thefitting parameter in Rietveld analysis performed at the occupancy ratiog of lower than 1.0, that is, lower than 100%, is S_(vacant). If S₁₀₀ isgreater than S_(vacant) (S₁₀₀>S_(vacant)), it is possible to determinethat a vacancy exists in the Na sites. Besides, the amount of vacancies(x-y) introduced in the Na sites can be estimated by further preciselyrefining the site occupancy ratio g. In this case, the site occupancyratio of a light element, such as Li, also need be determined.Therefore, it is preferable that the analysis be performed by usingneutron powder diffraction.

On the other hand, in order to determine the previously describedintensities I_(L) and I_(H) (I_(L1) and I_(H1)) of diffraction peaks forthe composite oxide, the powder X-ray diffraction results measured underthe above conditions without processing, i.e., raw data is used. Thepeak top, i.e., the maximum intensity of a strongest diffraction peakappearing within the range of 17°≦2θ≦18.5° is defined as I_(L). On theother hand, the peak top; i.e., the maximum intensity of a strongestdiffraction peak appearing within the range of 18.5°<2θ≦19.5° is definedas I_(H). An intensity ratio I_(L)/I_(H) can be calculated by dividingthe intensity numerical value (counts per second: cps) of the intensityI_(L) by the intensity numerical value (cps) of the intensity I_(H).

When the active material to be measured is contained in the electrodematerial of the nonaqueous electrolyte battery, first, the electrode istaken out from the nonaqueous electrolyte battery according to thepreviously described procedure. The taken-out and washed electrode iscut to the size almost equal to the area of the holder of a powder X-raydiffractometer, and used as the measurement sample.

The obtained measurement sample is affixed directly to the glass holder,and measured. In this case, the position of the peak originated from theelectrode substrate such as a metal foil is previously measured. Thepeaks of other components such as a conductive agent and a binder arealso previously measured. When the peaks of the substrate and activematerial overlap to each other, it is desirable that the layercontaining the active material (e.g., the below-described activematerial layer) is separated from the substrate, and subjected tomeasurement. This is a process for separating the overlapping peaks whenthe peak intensity is quantitatively measured. For example, the activematerial layer can be separated by irradiating the electrode substratewith an ultrasonic wave in a solvent. The active material layer isinserted into the capillary, mounted on the rotary sample table, andmeasured. As a result of this process, the XRD pattern of the activematerial can be obtained with the influence of the orientation reduced.

<Method for Confirming Composition of Composite Oxide>

The composition of the active material for a battery can be analyzedusing Inductively Coupled Plasma (ICP) emission spectrography, forexample. In this case, the abundance ratios of elements depend on thesensitivity of an analyzing device to be used. Therefore, when thecomposition of the active material for a battery as an example accordingto the first embodiment is analyzed, for example, using ICP emissionspectrography, the numerical values may deviate due to errors of themeasuring device from the previously described element ratios. However,even if the measurement results deviate as described above in the errorrange of the analyzing device, the active material for a battery as anexample according to the first embodiment can sufficiently exhibit thepreviously described effects.

In order to measure the composition of the active material for a batteryincluded in the battery according to ICP emission spectrography, thefollowing procedure is specifically performed. First, according to thepreviously described procedure, an electrode containing an activematerial to be measured is taken out from a nonaqueous electrolytebattery, and washed. The washed electrode is put in a suitable solvent,and irradiated with an ultrasonic wave. For example, an electrode is putinto ethyl methyl carbonate in a glass beaker and the glass beaker isvibrated in an ultrasonic washing machine, and thereby an electrodelayer containing an electrode active material can be separated from acurrent collector. Next, the separated electrode layer is dried underreduced pressure. The obtained electrode layer is ground in a mortar orthe like to provide a powder containing the target active material for abattery, conductive auxiliary agent, and binder or the like. Bydissolving the powder in an acid, a liquid sample containing the activematerial for a battery can be prepared. At this time, hydrochloric acid,nitric acid, sulfuric acid, and hydrogen fluoride or the like can beused as the acid. The composition of the active material for a batterycan be found by subjecting the liquid sample to ICP emissionspectrochemical analysis.

According to the first embodiment, the active material for a batterycontaining the composite oxide having the orthorhombic crystal structurecan be provided. The composite oxide is represented by the generalformula of Li_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O_(14+δ). The compositeoxide can exhibit a large potential change with a change of capacity ina potential range of 1.0 V (vs. Li/Li⁺) to 1.45 V (vs. Li/Li⁺). Inaddition, the average operating potential of the composite oxide can becontrolled by changing the Na amount. Further, the composite oxide canhave a crystal structure in which lithium ions are easily inserted intoand extracted from the crystal structure, and thus high reversiblecapacity during the charge-and-discharge and excellent life performancecan be realized. As a result, the active material for a batteryaccording to the first embodiment can realize a nonaqueous electrolytebattery which can exhibit a high energy density, a high battery voltage,and excellent life performance, and can provide a easy voltagemanagement.

Second Embodiment

According to a second embodiment, a nonaqueous electrolyte battery isprovided. The nonaqueous electrolyte battery includes a negativeelectrode containing the active material for a battery according to thefirst embodiment, a positive electrode, and a nonaqueous electrolyte.

The nonaqueous electrolyte battery according to the second embodimentcan further include a separator provided between the positive electrodeand the negative electrode. The positive electrode, the negativeelectrode, and the separator can constitute an electrode group. Thenonaqueous electrolyte may be held in the electrode group.

The nonaqueous electrolyte battery according to the second embodimentcan further include a container member accommodating the electrode groupand the nonaqueous electrolyte.

The nonaqueous electrolyte battery according to the second embodimentcan further include a positive electrode terminal electrically connectedto the positive electrode and a negative electrode terminal electricallyconnected to the negative electrode. At least a part of the positiveelectrode terminal and at least a part of the negative electrodeterminal may be extended to the outside of the container member.

Hereinafter, the negative electrode, the positive electrode, thenonaqueous electrolyte, the separator, the container member, thepositive electrode terminal, and the negative electrode terminal will bedescribed in detail.

1) Negative Electrode

The negative electrode can contain a current collector, and a negativeelectrode layer (a negative electrode active material-containing layer).The negative electrode layer can be formed on one or both surfaces ofthe current collector. The negative electrode layer can contain anegative electrode active material, and optionally a conductive agentand a binder.

The active material for a battery according to the first embodiment canbe contained in the negative electrode layer as a negative electrodeactive material. The negative electrode using the active material for abattery according to the first embodiment can exhibit a low electrodepotential in which the potential is continuously changed within apotential range of 1.45 V (vs. Li/Li⁺) to 1.0 V (vs. Li/Li⁺). In thenegative electrode using the active material for a battery according tothe first embodiment, the average operating potential can be controlled,as described above. Further, the active material for a battery accordingto the first embodiment can exhibit a high reversible capacity duringthe charge-and-discharge and excellent life performance, as describedabove. For those reasons, the nonaqueous electrolyte battery accordingto the second embodiment which contains such a negative electrode canexhibit a high energy density, a high battery voltage, and excellentlife performance, and can provide easy voltage management.

In the negative electrode, the active material for a battery accordingto the first embodiment may be singly used as the negative electrodeactive material, but a mixture prepared by mixing the active materialfor a battery according to the first embodiment with another activematerial may also be used. Examples of other active materials includelithium titanate having a ramsdellite structure (e.g., Li₂Ti₃O₇),lithium titanate having a spinel structure (e.g., Li₄Ti₅O₁₂), monoclinictype titanium dioxide (TiO₂ (B)), anatase type titanium dioxide, rutiletype titanium dioxide, a hollandite-type titanium composite oxide, and amonoclinic type niobium titanium composite oxide (e.g., Nb₂TiO₇).

The conductive agent is added to improve a current collectionperformance and to suppress the contact resistance between the negativeelectrode active material and the current collector. Examples of theconductive agent include carbonaceous substances such as vapor growncarbon fiber (VGCF), acetylene black, carbon black, and graphite.

The binder is added to fill gaps in the dispersed negative electrodeactive material and also to bind the negative electrode active materialwith the current collector. Examples of the binder includepolytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorinerubber, styrene-butadiene rubber, a polyacrylic acid compound, and animide compound.

The blending ratios of the active material, conductive agent and binderin the negative electrode layer are preferably 68% by mass to 96% bymass, 2% by mass to 30% by mass, and 2% by mass to 30% by mass,respectively. When the content of the conductive agent is 2% by mass ormore, the current collection performance of the negative electrode layercan be improved. When the content of the binder is 2% by mass or more,binding between the negative electrode layer and current collector issufficiently achieved, and excellent cycling characteristics can beexpected. On the other hand, each of the contents of the conductiveagent and binder is preferably 28% by mass or less, thereby increasingthe capacity.

As the current collector, a material which is electrochemically stableat the lithium insertion and extraction potential of the negativeelectrode active material is used. The current collector is preferablymade of copper, nickel, stainless steel or aluminum, or an aluminumalloy containing one or more elements selected from Mg, Ti, Zn, Mn, Fe,Cu, and Si. The thickness of the current collector is preferably 5 to 20μm. The current collector having such a thickness can keep a balancebetween the strength and weight reduction of the negative electrode.

By using the active material for a battery according to the firstembodiment, the density of the negative electrode layer (excluding thecurrent collector) can be set to the range of 1.8 g/cm³ to 2.8 g/cm³.The negative electrode in which the density of the negative electrodelayer is within the range can exhibit an excellent energy density andexcellent electrolytic solution holdablility. More preferably, thedensity of the negative electrode layer is 2.1 g/cm³ to 2.6 g/cm³.

The negative electrode is produced by, for example, suspending anegative electrode active material, a binder, and a conductive agent inan ordinary solvent to prepare a slurry, applying the slurry to acurrent collector, drying the coating to form a negative electrodelayer, and then pressing the layer. Alternatively, the negativeelectrode may be also produced by forming a negative electrode activematerial, a binder, and a conductive agent into pellets to produce anegative electrode layer, and placing it on a current collector.

2) Positive Electrode

The positive electrode can include a current collector and a positiveelectrode layer (positive electrode active material-containing layer).The positive electrode layer may be formed on one or both surfaces ofthe current collector. The positive electrode layer can include apositive electrode active material, and optionally a conductive agentand a binder.

The positive electrode active material may be, for example, an oxide ora sulfide. Examples of the oxide and sulfide include a compound capableof inserting and extracting lithium. Specific examples thereof includemanganese dioxide (MnO₂), iron oxide, copper oxide, nickel oxide,lithium manganese composite oxide (e.g., Li_(x)Mn₂O₄ or Li_(x)MnO₂),lithium nickel composite oxide (e.g., Li_(x)NiO₂), lithium cobaltcomposite oxide (e.g., Li_(x)CoO₂), lithium nickel cobalt compositeoxide (e.g., LiNi_(1−y)Co_(y)O₂), lithium manganese cobalt compositeoxide (e.g., Li_(x)Mn_(y)Co_(1−y)O₂), lithium manganese nickel compositeoxide having a spinel structure (e.g., Li_(x)Mn_(2−y)Ni_(y)O₄), lithiumphosphorus oxide having an olivine structure (e.g., Li_(x)FePO₄,Li_(x)Fe_(1−y)Mn_(y)PO₄, and Li_(x)C_(o)PO₄), iron sulfate [Fe₂(SO₄)₃],vanadium oxide (e.g., V₂O₅), and lithium nickel cobalt manganesecomposite oxide. In the above-described formula, 0<x≦1, and 0<y≦1. Asthe active material, one of these compounds may be used singly, orcombination of two or more of the compounds can be used.

More preferred examples of the positive electrode active materialinclude lithium manganese composite oxide having a high positiveelectrode voltage (e.g., Li_(x)Mn₂O₄), lithium nickel composite oxide(e.g., Li_(x)NiO₂), lithium cobalt composite oxide (e.g.,Li_(x)C_(o)O₂), lithium nickel cobalt composite oxide (e.g.,LiNi_(1−y)Co_(y)O₂), lithium manganese nickel composite oxide having aspinel structure (e.g., Li_(x)Mn_(2−y)Ni_(y)O₄), lithium manganesecobalt composite oxide (e.g., Li_(x)Mn_(y)Co_(1−y)O₂), lithium ironphosphate (e.g., Li_(x)FePO₄), and lithium nickel cobalt manganesecomposite oxide. In the above-described formula, 0<x≦1, and 0<y≦1.

When an ordinary-temperature molten salt is used as the nonaqueouselectrolyte of the battery, preferred examples of the positive electrodeactive material include lithium iron phosphate, Li_(x)VPO₄F (0≦x≦1),lithium manganese composite oxide, lithium nickel composite oxide, andlithium nickel cobalt composite oxide. Since these compounds have lowreactivity with ordinary-temperature molten salts, they can improve thecycle life.

The primary particle size of the positive electrode active material ispreferably 100 nm to 1 μm. The positive electrode active material havinga primary particle size of 100 nm or more is easy to handle duringindustrial production. The positive electrode active material having aprimary particle size of 1 μm or less can allow lithium ions to smoothlydiffuse in solids.

The specific surface area of the positive electrode active material ispreferably 0.1 m²/g to 10 m²/g. The positive electrode active materialhaving a specific surface area of 0.1 m²/g or more can secure sufficientsites in which lithium ions can be inserted and extracted. The positiveelectrode active material having a specific surface area of 10 m²/g orless is easy to handle during industrial production, and can secure agood charge-and-discharge cycle performance.

The binder is added to bind the positive electrode active material withthe current collector. Examples of the binder includepolytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorinerubber, a polyacrylic acid compound, and an imide compound.

The conductive agent is as necessary added to improve the currentcollection performance, and to suppress the contact resistance betweenthe positive electrode active material and current collector. Examplesof the conductive agent include carbonaceous substances such asacetylene black, carbon black and graphite.

In the positive electrode layer, the blending ratios of the positiveelectrode active material and binder are preferably 80% by mass to 98%by mass, and 2% by mass to 20% by mass, respectively.

When the binder content is 2% by mass or more, sufficient electrodestrength can be achieved. When the binder content is 20% by mass orless, the loading of the insulator in the electrode can be reduced, andthereby the internal resistance can be decreased.

When a conductive agent is added, the blending ratios of the positiveelectrode active material, binder, and conductive agent are preferably77% by mass to 95% by mass, 2% by mass to 20% by mass, and 3% by mass to15% by mass, respectively. When the content of the conductive agent is3% by mass or more, the above-described effects can be achieved. Bysetting the amount of the positive electrode conductive agent to 15% bymass or less, the decomposition of a nonaqueous electrolyte on thesurface of the positive electrode conductive agent in high-temperaturestorage can be reduced.

The current collector is preferably an aluminum foil, or an aluminumalloy foil containing one or more elements selected from Mg, Ti, Zn, Ni,Cr, Mn, Fe, Cu, and Si.

The thickness of the aluminum foil or aluminum alloy foil is preferably5 μm to 20 μm, and more preferably 15 μm or less. The purity of thealuminum foil is preferably 99% by mass or more. The content of thetransition metal such as iron, copper, nickel, or chromium contained inthe aluminum foil or aluminum alloy foil is preferably 1% by mass orless.

The positive electrode is produced by, for example, suspending apositive electrode active material, a binder, and as necessary aconductive agent in an appropriate solvent to prepare a slurry, applyingthe slurry to a positive electrode current collector, drying the coatingto form a positive electrode layer, and then pressing the layer.Alternatively, the positive electrode may be also produced by forming anactive material, a binder, and as necessary a conductive agent intopellets to produce a positive electrode layer, and placing it on acurrent collector.

3) Nonaqueous Electrolyte

The nonaqueous electrolyte may be, for example, a liquid nonaqueouselectrolyte which is prepared by dissolving an electrolyte in an organicsolvent, or gel-like nonaqueous electrolyte which is a composite of aliquid electrolyte and a polymer material.

The liquid nonaqueous electrolyte is preferably prepared by dissolvingan electrolyte in an organic solvent in the concentration of 0.5 mol/Lto 2.5 mol/L.

Examples of the electrolyte include lithium salts such as lithiumperchlorate (LiClO₄), lithium hexafluorophosphate (LiPF₆), lithiumtetrafluoroborate (LiBF₄), lithium hexafluoroarsenate (LiASF₆), lithiumtrifluoromethanesulfonate (LiCF₃SO₃), and lithiumbistrifluoromethylsulfonylimide [LiN(CF₃SO₂)₂], and mixtures thereof.The electrolyte is preferably resistant to oxidation even at a highpotential, and most preferably LiPF₆.

Examples of the organic solvent include a cyclic carbonate such aspropylene carbonate (PC), ethylene carbonate (EC), or vinylenecarbonate; a chain carbonate such as diethyl carbonate (DEC), dimethylcarbonate (DMC), or methyl ethyl carbonate (MEC); a cyclic ether such astetrahydrofuran (THF), 2-methyl tetrahydrofuran (2MeTHF), or dioxolane(DOX); a chain ether such as dimethoxy ethane (DME) or diethoxy ethane(DEE); γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane (SL). Oneof these organic solvents can be used alone or a mixed solvent can beused.

Examples of the polymeric material include polyvinylidene fluoride(PVdF), polyacrylonitrile (PAN), and polyethylene oxide (PEO).

Alternatively, the nonaqueous electrolyte may be, for example, anordinary-temperature molten salt (ionic melt) containing lithium ions, apolymer solid electrolyte, or an inorganic solid electrolyte.

The ordinary-temperature molten salt (ionic melt) means compounds whichcan exist in a liquid state at ordinary temperature (15 to 25° C.) amongorganic salts constituted of combinations of organic cations and anions.The ordinary-temperature molten salt includes an ordinary-temperaturemolten salt which exists alone as a liquid, an ordinary-temperaturemolten salt which becomes a liquid after being mixed with anelectrolyte, and an ordinary-temperature molten salt which becomes aliquid after being dissolved in an organic solvent. In general, themelting point of the ordinary-temperature molten salt used in nonaqueouselectrolyte batteries is 25° C. or below. The organic cations generallyhave a quaternary ammonium skeleton.

The polymer solid electrolyte is prepared by dissolving the electrolytein a polymeric material, and solidifying it.

The inorganic solid electrolyte is a solid substance having lithium ionconductivity.

4) Separator

The separator may be made of, for example, a porous film or syntheticresin nonwoven fabric containing polyethylene, polypropylene, cellulose,or polyvinylidene fluoride (PVdF). Among these, a porous film containingpolyethylene or polypropylene can improve safety because the porous filmmelts at a fixed temperature to be able to shut off a current.

5) Container Member

The container member may be, for example, a laminate film having athickness of 0.5 mm or less, or a metal case having a wall thickness of1 mm or less. The thickness of the laminate film is more preferably 0.2mm or less. The wall thickness of the metal case is more preferably 0.5mm or less, and still more preferably 0.2 mm or less.

The shape of the container member is not particularly limited, and maybe, for example, flat (thin), square, cylinder, coin, or button-shaped.The container member depends on the size of the battery, and may be thatfor a compact battery mounted on mobile electronic devices, and a largebattery mounted on two- to four-wheel automobiles.

The laminate film used herein is a multilayer film including resinlayers and a metal layer sandwiched between the resin layers. The metallayer is preferably an aluminum foil or an aluminum alloy foil forreducing weight. The resin layer may be, for example, a polymericmaterial such as polypropylene (PP), polyethylene (PE), nylon, orpolyethylene terephthalate (PET). The laminate film may be heat-sealedto be formed into the shape of a container member.

The metal case is made of aluminum or an aluminum alloy, for example. Asthe aluminum alloy, an alloy containing an element such as magnesium,zinc, or silicon is preferable. If a transition metal such as iron,copper, nickel, or chromium is contained in the alloy, the contentthereof is preferably set to 1% by mass or less.

6) Positive Electrode Terminal and Negative Electrode Terminal

The positive electrode terminal may be made of, for example, a materialwhich is electrically stable in the potential range of 3 V to 5 V basedon the oxidation-reduction potential of lithium, and has electricalconductivity. Specifically, the positive electrode terminal is made ofaluminum or an aluminum alloy containing Mg, Ti, Zn, Mn, Fe, Cu, and Sior the like. The positive electrode terminal is preferably made of thesame material as the positive electrode current collector in order toreduce contact resistance with the positive electrode current collector.

The negative electrode terminal may be made of a material which iselectrochemically stable at the potential at which the negativeelectrode active material described above inserts and extracts Li, andhas electrical conductivity. Specific examples of the material for thenegative electrode terminal include copper, nickel, stainless steel, oraluminum. The negative electrode terminal is preferably made of the samematerial as the negative electrode current collector in order to reducethe contact resistance with the negative electrode current collector.

Next, the nonaqueous electrolyte battery according to the secondembodiment will be more specifically described with reference to thedrawings.

First, a nonaqueous electrolyte battery as an example according to thesecond embodiment will be described with reference to FIGS. 3 and 4.

FIG. 3 is a cross sectional view of a nonaqueous electrolyte battery asan example according to the second embodiment. FIG. 4 is an enlargedcross sectional view showing a portion A in FIG. 3.

A nonaqueous electrolyte battery 10 shown in FIGS. 3 and 4 includes abag-shaped container member 2 shown in FIG. 3, an electrode group 1shown in FIGS. 3 and 4, and a nonaqueous electrolyte (not shown). Theelectrode group 1 and the nonaqueous electrolyte are accommodated in thecontainer member 2. The nonaqueous electrolyte is held in the electrodegroup 1.

The bag-shaped container member 2 is made of a laminate film includingtwo resin layers and a metal layer sandwiched between the resin layers.

As shown in FIG. 3, the electrode group 1 is a coiled electrode group ina flat form. The coiled electrode group 1 in a flat form is formed by,as shown in FIG. 4, spirally winding a laminate which includes, from theoutside to the inside, a negative electrode 3, a separator 4, a positiveelectrode 5, and a separator 4, and then press-forming the woundlaminate.

The negative electrode 3 includes a negative electrode current collector3 a and a negative electrode layer 3 b. The negative electrode layer 3 bcontains the active material for a battery according to the firstembodiment. The negative electrode 3 in the outermost layer has aconfiguration in which a negative electrode layer 3 b is formed on oneside which is the internal surface of a negative electrode currentcollector 3 a as shown in FIG. 4. In the other portion of the negativeelectrode 3, the negative electrode layers 3 b are formed on bothsurfaces of the negative electrode current collector 3 a.

The positive electrode 5 includes a positive electrode current collector5 a and positive electrode layers 5 b formed on both surfaces of thepositive electrode current collector 5 a.

As shown in FIG. 3, in the vicinity of the outer peripheral edge of thecoiled electrode group 1, a negative electrode terminal 6 is connectedto the negative electrode current collector 3 a in the outermostnegative electrode 3, and a positive electrode terminal 7 is connectedto the positive electrode current collector 5 a in the inside positiveelectrode 5. The negative electrode terminal 6 and the positiveelectrode terminal 7 are extended out from the opening of the bag-shapedcontainer member 2.

The nonaqueous electrolyte battery 10 shown in FIGS. 3 and 4 can beproduced according to the following procedure, for example. First, anelectrode group 1 is produced. The electrode group 1 is then enclosed ina bag-shaped container member 2. In this case, one ends of a negativeelectrode terminal 6 and positive electrode terminal 7 are protrudedtoward the outside of the container member 2. Next, the circumference ofthe container member 2 is heat-sealed while a part thereof remainsunsealed. Next, for example, a liquid nonaqueous electrolyte is injectedvia the opening of the bag-shaped container member 2 which is notheat-sealed. Finally, the opening is heat-sealed, and thereby the coiledelectrode group 1 and the liquid state nonaqueous electrolyte arecompletely sealed.

The nonaqueous electrolyte battery according to the second embodiment isnot limited to the nonaqueous electrolyte battery as an example shown inFIGS. 3 and 4, and may be, for example, a battery having a structureshown in FIGS. 5 and 6.

FIG. 5 is a partially cutaway perspective view schematically showing anonaqueous electrolyte battery as another example according to thesecond embodiment. FIG. 6 is an enlarged cross sectional view showing aportion B in FIG. 5.

A nonaqueous electrolyte battery 10 shown in FIGS. 5 and 6 includes anelectrode group 11 shown in FIGS. 5 and 6, a container member 12 shownin FIG. 5, and a nonaqueous electrolyte (not shown). The electrode group11 and the nonaqueous electrolyte are accommodated in the containermember 12. The nonaqueous electrolyte is held in the electrode group 11.

The container member 12 is made of a laminate film including two resinlayers and a metal layer sandwiched between the resin layers.

As shown in FIG. 6, the electrode group 11 is a stacked electrode group.As shown in FIG. 6, the stacked electrode group 11 has a structure inwhich positive electrodes 13 and negative electrodes 14 are alternatelylaminated with a sandwiched therebetween.

The electrode group 11 includes a plurality of positive electrodes 13.Each of the plurality of positive electrodes 13 includes a positiveelectrode current collector 13 a, and a positive electrode layer 13 bsupported on each of the both surfaces of the positive electrode currentcollector 13 a. The electrode group 11 includes a plurality of negativeelectrodes 14. Each of the plurality of negative electrodes 14 includesa negative electrode current collector 14 a, and a negative electrodelayer 14 b supported on each of the both surfaces of the negativeelectrode current collector 14 a. A part of the negative electrodecurrent collector 14 a of each of the negative electrodes 14 protrudesat one side from the negative electrode 14. The protruded part of thenegative electrode current collector 14 a is electrically connected to astrip-shaped negative electrode terminal 16. The tip of the strip-shapednegative electrode terminal 16 is extended out from the container member12. Although not shown in the drawings, a part of the positive electrodecurrent collector 13 a of the positive electrode 13 protrudes from thepositive electrode 13 at the side opposed to the protruded side of thenegative electrode current collector 14 a. The protruded part of thepositive electrode current collector 13 a from the positive electrode 13is electrically connected to a strip-shaped positive electrode terminal17. The tip of the strip-shaped positive electrode terminal 17 isopposed to the negative electrode terminal 16, and extended out from aside of the container member 12.

The nonaqueous electrolyte battery according to the second embodimentcontains the active material for a battery according to the firstembodiment. The nonaqueous electrolyte battery according to the secondembodiment, accordingly, can exhibit a high energy density, a highbattery voltage, and excellent life performance, and can provide easyvolatege management.

Third Embodiment

According to a third embodiment, there is provided a battery pack. Thebattery pack includes the nonaqueous electrolyte battery according tothe second embodiment.

The battery pack according to the third embodiment can include one ormore nonaqueous electrolyte batteries (unit cells) according to thesecond embodiment described above. The plurality of nonaqueouselectrolyte batteries which may be included in the battery packaccording to the third embodiment can be electrically connected inseries or parallel, to constitute a battery module. The battery packaccording to the third embodiment may include a plurality of batterymodules.

Next, a battery pack as an example according to the third embodimentwill be described with reference to the drawings.

FIG. 7 is an exploded perspective view of the battery pack as an exampleaccording to the third embodiment. FIG. 8 is a block diagram showing anelectric circuit of the battery pack of FIG. 7.

A battery pack 20 shown in FIGS. 7 and 8 includes a plurality of unitcells 21. Each of the plurality of unit cells 21 is flat nonaqueouselectrolyte battery 10 described with reference to FIGS. 3 and 4.

The plurality of unit cells 21 are stacked so that the negativeelectrode terminal 6 and the positive electrode terminal 7 extendedoutside are arranged in the same direction, and fastened with anadhesive tape 22 to constitute a battery module 23. The unit cells 21are electrically connected to each other in series as shown in FIG. 8.

A printed wiring board 24 is arranged opposed to the side plane wherethe negative electrode terminal 6 and the positive electrode terminal 7of the unit cell 21 are extended. A thermistor 25, a protective circuit26, and an energizing terminal 27 to an external device are mounted onthe printed wiring board 24 as shown in FIG. 8. An electric insulatingplate (not shown) is attached to the surface of the printed wiring board24 facing the battery module 23 to avoid unnecessary connection of thewires of the battery module 23.

A positive electrode-side lead 28 is connected to the positive electrodeterminal 7 located at the bottom layer of the battery module 23 and thedistal end of the lead 28 is inserted into a positive electrode-sideconnector 29 of the printed wiring board 24 so as to be electricallyconnected. An negative electrode-side lead 30 is connected to thenegative electrode terminal 6 located at the top layer of the batterymodule 23 and the distal end of the lead 30 is inserted into an negativeelectrode-side connector 31 of the printed wiring board 24 so as to beelectrically connected. The connectors 29 and 31 are connected to theprotective circuit 26 through wirers 32 and 33 formed in the printedwiring board 24.

The thermistor 25 detects the temperature of the unit cells 21 and thedetection signal is sent to the protective circuit 26. The protectivecircuit 26 can shut down a plus-side wirer 34 a and a minus-side wirer34 b between the protective circuit 26 and the energizing terminal 27 toan external device under a predetermined condition. The predeterminedcondition indicates, for example, the case where the temperaturedetected by the thermistor 25 becomes a predetermined temperature ormore. Another example of the predetermined condition indicates the casewhere the over-charge, over-discharge, or over-current of the unit cells21 is detected. The detection of the over-charge and the like isperformed on each of the unit cells 21 or the whole of the batterymodule 23. When each of the unit cells 21 is detected, the cell voltagemay be detected, or positive electrode or negative electrode potentialmay be detected. In the case of the latter, a lithium electrode to beused as a reference electrode is inserted into each of the unit cells21. In the case of the battery pack 20 of FIGS. 7 and 8, wirers 35 forvoltage detection are connected to each of the unit cells 21. Detectionsignals are sent to the protective circuit 26 through the wirers 35.

Protective sheets 36 including rubber or resin are arranged on threeside planes of the battery module 23 except the side plane from whichthe positive electrode terminal 7 and the negative electrode terminal 6are protruded.

The battery module 23 is housed in a housing container 37 together witheach of the protective sheets 36 and the printed wiring board 24. Thatis, the protective sheets 36 are arranged on both internal surfaces in along side direction and on one internal surface in a short sidedirection of the housing container 37. The printed wiring board 24 isarranged on the other internal surface in a short side direction. Thebattery module 23 is located in a space surrounded by the protectivesheets 36 and the printed wiring board 24. A lid 38 is attached to theupper surface of the housing case 37.

In order to fix the battery module 23, a heat-shrinkable tape may beused in place of the adhesive tape 22. In this case, the battery moduleis bound by placing the protective sheets on the both sides of thebattery module, revolving the heat-shrinkable tape, and thermallyshrinking the heat-shrinkable tape.

In FIGS. 7 and 8, the structure in which the unit cells 21 are connectedto each other in series is shown. In order to increase the batterycapacity, the unit cells may be connected to each other in parallel.Furthermore, the assembled battery packs can be connected to each otherin series and/or in parallel.

The aspect of the battery pack according to the third embodiment may beappropriately changed depending on its application. The applications ofthe battery pack according to the third embodiment are preferably thosefor which cycle characteristics when large-current is taken out aredesired. Specific examples of these applications include application asa battery of a digital camera and application to a vehicle such as atwo- or four-wheeled hybrid electric vehicle, a two- or four-wheeledelectric vehicle or a power-assisted bicycle. Particularly preferably,the battery pack according to the third embodiment is used for a batterymounted to a vehicle.

The battery pack according to the third embodiment includes thenonaqueous electrolyte battery according to the second embodiment.Therefore, the battery pack according to the third embodiment canexhibit a high energy density and a high battery voltage, exhibitexcellent life performance, and can provide easy voltage management.

Fourth Embodiment

According to a fourth embodiment, there is provided a battery module.The battery module includes nonaqueous electrolyte batteries. Each ofthe nonaqueous electrolyte batteries is the nonaqueous electrolytebattery according to the second embodiment. The nonaqueous electrolytebatteries are electrically connected in series.

The battery module according to the fourth embodiment can furtherinclude a lead for electrically connecting the plurality of nonaqueouselectrolyte batteries to each other. The lead is preferably made of thesame material as that of a terminal of the nonaqueous electrolytebattery in order to reduce contact resistance with the terminal of thenonaqueous electrolyte battery with which the lead is connected, forexample.

For example, the battery module as an example according to the fourthembodiment can include five nonaqueous electrolyte batteries. Asdescribed above, the nonaqueous electrolyte battery according to thesecond embodiment can exhibit a high battery voltage. Therefore, thebattery module including the five nonaqueous electrolyte batteriesaccording to the second embodiment connected to each other in series canshow the same operating voltage as that of a lead storage battery, forexample.

Alternatively, a battery module as another example according to thefourth embodiment can include six nonaqueous electrolyte batteries.

The battery pack according to the third embodiment can include thebattery module according to the fourth embodiment.

Next, the battery module as an example according to the fourthembodiment will be described in more detail with reference to thedrawings.

FIG. 9 is a schematic perspective view of a battery module as an exampleaccording to the fourth embodiment. A battery module 23 shown in FIG. 9includes five unit cells 21. Each of the five unit cells 21 is thesquare type nonaqueous electrolyte battery as an example according tothe second embodiment.

The battery module 23 shown in FIG. 9 further includes four leads 40. Alead 40 connects a negative electrode terminal 6 of one unit cell 21 anda positive electrode terminal 7 of another unit cell 21. Thus, the fiveunit cells 21 are electrically connected to each other in series via thefour leads 40. That is, the battery module 23 of FIG. 9 is a batterymodule including the five unit cells connected in series.

As shown in FIG. 9, the positive electrode terminal 7 of one unit cell21 among the five unit cells 21 is connected to a positiveelectrode-side lead 28 for external connection. The negative electrodeterminal 6 of another unit cell 21 among the five unit cells 21 isconnected to a negative electrode-side lead 30 for external connection.

Since the battery module according to the fourth embodiment includes thenonaqueous electrolyte batteries each of which is one according to thesecond embodiment, the battery module can provide easycharge-and-discharge management, exhibit excellent life performance, andexhibit a high energy density and a high battery voltage.

EXAMPLES

Hereinafter, the above embodiments are explained in more detailreferring to Examples. The identification of a crystal phase and theestimation of a crystal structure of each of synthesized products wasperformed by powder X-ray diffraction using Cu—Kα rays. In addition, acomposition of a product was analyzed by an ICP method to confirm that atarget product was obtained.

(Synthesis)

Example A Examples A-1 to A-13

In Example A-1 to A-13, products of Examples A-1 to A-13 weresynthesized according to the following procedures. Target compositionsof Examples A-1 to A-13 are shown in the following Table 1.

First, commercially available oxide and carbonate reagents shown in thefollowing Table 1 were provided as starting materials so that molarratios shown in Table 1 were satisfied and the total weight was 50 g.Since the vaporized amount corresponding to 3% was confirmed as theamount of lithium carbonate as a result of analyzing the vaporizedamount of lithium ions during firing in a preliminary experiment,lithium carbonate was provided in a higher amount than that of thetarget composition by 3%.

Next, the starting materials, provided as above, were mixed, and themixture was put in an agate pod (a volume of 300 ml) for a ball mill.Agate balls having a diameter of 10 mm or 5 mm were put in the pod in aratio of the number of balls of 1:1 up to one third of the pod volume.After that, 50 ml of ethanol was added to the pod, and the mixture waswet-mixed at 120 rpm for 60 minutes to obtain a mixture. When thestarting materials are uniformly mixed by the wet-mixing, and thus atarget single phase of a crystal phase can be obtained.

Next, the thus obtained mixture was put in an electric furnace, and aheat treatment was performed by the following procedures.

First, calcination was performed at a temperature of 650° C. for 6 hoursin an air atmosphere. Next, a powder obtained by calcination was takenout from the furnace, and the powder was reground and mixed. When thecalcination is previously performed as above to decompose the carbonatesor the like in the materials and they are mixed again, the raw materialparticles can cohere to each other in a main sintering; as a result,particles which are uniform and have high crystallinity can be obtained.

The thus obtained mixture was subsequently subjected to afirst-sintering at a temperature of 900° C. for 6 hours. After thesintering, the sintered powder was taken out from the furnace, and thesinetered powder was mixed again.

Subsequently, the re-mixed sintered powder was put in the furnace, and asecond sintering was performed at a temperature of 900° C. for 6 hoursin an air atmosphere. After that, the temperature in the electricfurnace was kept at 400° C. for 2 hours, and then was quickly cooled toroom temperature. Next, the sintered powder was taken out from thefurnace, and the sintered powder was mixed again. The powder obtainedafter the second sintering, i.e., as a result of sintering at atemperature of 900° C. for a total of 12 hours was used as each ofproducts was used as each of products of Example A-1 to A-13.

Example A-14

In Example A-14, a product of Example A-14 was synthesized in the samemanner as in Example A-5 except that the sintering was performed in areduction atmosphere by blowing nitrogen gas containing 3% hydrogen intothe electric furnace.

TABLE 1 Li Na M1 Ti M2 Source/ Source/ Source/ Source/ Source/ A seriesTarget Composition Amount Amount Amount Amount Amount ComparativeLi₂Na₂Ti₆O₁₄ Li₂CO₃/1.0 Na₂CO₃/1.0 — TiO₂/6.0 — Example A-1a ComparativeLi₂Na₂Ti₆O₁₄ Li₂CO₃/1.0 Na₂CO₃/1.0 — TiO₂/6.0 — Example A-1b ComparativeLi_(2.1)Na_(1.9)Ti₆O₁₄ Li₂CO₃/1.05 Na₂CO₃/0.95 — TiO₂/6.0 — Example A-2Comparative Li₂Na₂Ti_(5.9)Nb_(0.1)O₁₄ Li₂CO₃/1.0 Na₂CO₃/1.0 — TiO₂/5.9Nb₂O₅/0.05 Example A-3 Comparative Li₂MgTi₆O₁₄ Li₂CO₃/1.0 — MgO/1.0TiO₂/6.0 — Example A-4 Comparative Li₂BaTi_(5.9)Al_(0.1)O₁₄ Li₂CO₃/1.0 —BaCO₃/1.0 TiO₂/5.9 Al₂O₃/0.05 Example A-5 Example A-1Li₂Na_(1.99)Ti_(5.99)Nb_(0.01)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.995 — TiO₂/5.99Nb₂O₅/0.005 Example A-2 Li₂Na_(1.95)Ti_(5.95)Nb_(0.05)O₁₄ Li₂CO₃/1.0Na₂CO₃/0.975 — TiO₂/5.95 Nb₂O₅/0.025 Example A-3Li₂Na_(1.9)Ti_(5.9)Nb_(0.1)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.95 — TiO₂/5.9Nb₂O₅/0.05 Example A-4 Li₂Na_(1.75)Ti_(5.75)Nb_(0.25)O₁₄ Li₂CO₃/1.0Na₂CO₃/0.875 — TiO₂/5.75 Nb₂O₅/0.125 Example A-5Li₂Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.75 — TiO₂/5.50Nb₂O₅/0.25 Example A-6 Li₂Na_(1.25)Ti_(5.25)Nb_(0.75)O₁₄ Li₂CO₃/1.0Na₂CO₃/0.625 — TiO₂/5.25 Nb₂O₅/0.375 Example A-7Li₂Na_(1.1)Ti_(5.1)Nb_(0.9)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.55 — TiO₂/5.10Nb₂O₅/0.45 Example A-8 Li₂Na_(1.05)Ti_(5.05)Nb_(0.95)O₁₄ Li₂CO₃/1.0Na₂CO₃/0.525 — TiO₂/5.05 Nb₂O₅/0.475 Example A-9Li₂Na_(1.01)Ti_(5.01)Nb_(0.99)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.505 — TiO₂/5.01Nb₂O₅/0.495 Example A-10 Li_(2.1)Na_(1.99)Ti_(5.99)Nb_(0.01)O₁₄Li₂CO₃/1.05 Na₂CO₃/0.995 — TiO₂/5.99 Nb₂O₅/0.005 Example A-11Li_(2.5)Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄ Li₂CO₃/1.25 Na₂CO₃/0.75 — TiO₂/5.50Nb₂O₅/0.25 Example A-12 Li₄Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄ Li₂CO₃/2.00Na₂CO₃/0.75 — TiO₂/5.50 Nb₂O₅/0.25 Example A-13Li₆Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄ Li₂CO₃/3.00 Na₂CO₃/0.75 — TiO₂/5.50Nb₂O₅/0.25 Example A-14 Li₂Na_(1.5)Ti_(5.5)Nb_(0.5)O_(13.5) Li₂CO₃/1.00Na₂CO₃/0.75 — TiO₂/5.50 Nb₂O₅/0.25

Comparative Examples A-1 to A-5

In Comparative Example A-1, in order to show that an intensity ratio ofthe powder X-ray diffraction diagram varies depending on the synthesiscondition, products of Comparative Examples A-1a and A-1b, whose targetcomposition was compound Li₂Na₂Ti₆O₁₄, were synthesized under differenttwo conditions. In Comparative Example A-1a, a product of ComparativeExample A-1a was synthesized in the same manner as in Example A-1 exceptthat starting materials containing no M2 source, as shown in Table 1,were used, and the sintering was continuously performed at 1000° C. for24 hours without considering the Li vaporization amount during thesintering. On the other hand, in Comparative Example A-1b, a product ofComparative Example A-1b was synthesized in the same manner as inExample A-1 except that starting materials containing no M2 source asshown in Table 1 were used.

In Comparative Example A-2, a product of Comparative Example A-2 wassynthesized in the same manner as in Comparative Example A-1b exceptthat amounts of lithium carbonate and sodium carbonate were changed tothose described in Table 1.

In Comparative Example A-3, a product of Comparative Example A-3 wassynthesized in the same manner as in Comparative Example A-1b exceptthat starting materials shown in Table 1 were used.

In Comparative Examples A-4 and A-5, products of Comparative ExamplesA-4 and A-5 were synthesized in the same manner as in Example A-1 exceptthat the target compositions were to be those described inElectrochemistry Communications 11 (2009) pp. 1251-1254. The targetcompositions, the starting materials and the molar ratios were asdescribed in the above Table 1.

(Confirmation of Composition of Product)

The compositions of the products of Examples A-1 to A-14 and theproducts of Comparative Examples A-1 to A-5 were analyzed according tothe ICP method described above. The results are shown in Table 2 below.

As shown in Table 2, the product of Example A-14 had a subscript ofoxygen in the composition formula of 13.5. In the product of ExampleA-14, accordingly, oxygen deficiency occurred slightly compared toExample A-5.

TABLE 2 Li_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O₁₄ A series Composition w xy z Comparative Li₂Na₂Ti₆O₁₄ 0 0 0 0 Example A-1a ComparativeLi₂Na₂Ti₆O₁₄ 0 0 0 0 Example A-1b Comparative Li_(2.1)Na_(1.9)Ti₆O₁₄ 0.10.1 0 0 Example A-2 Comparative Li₂Na₂Ti_(5.9)Nb_(0.1)O₁₄ 0 0 0 0.1Example A-3 Comparative Li₂MgTi₆O₁₄ 0 — 0 0 Example A-4 ComparativeLi₂BaTi_(5.9)Al_(0.1)O₁₄ 0 — 0 0.1 Example A-5 Example A-1Li₂Na_(1.99)Ti_(5.99)Nb_(0.01)O₁₄ 0 0.01 0 0.01 Example A-2Li₂Na_(1.95)Ti_(5.95)Nb_(0.05)O₁₄ 0 0.05 0 0.05 Example A-3Li₂Na_(1.9)Ti_(5.9)Nb_(0.1)O₁₄ 0 0.1 0 0.1 Example A-4Li₂Na_(1.75)Ti_(5.75)Nb_(0.25)O₁₄ 0 0.25 0 0.25 Example A-5Li₂Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄ 0 0.5 0 0.5 Example A-6Li₂Na_(1.25)Ti_(5.25)Nb_(0.75)O₁₄ 0 0.75 0 0.75 Example A-7Li₂Na_(1.1)Ti_(5.1)Nb_(0.9)O₁₄ 0 0.9 0 0.9 Example A-8Li₂Na_(1.05)Ti_(5.05)Nb_(0.95)O₁₄ 0 0.95 0 0.95 Example A-9Li₂Na_(1.01)Ti_(5.01)Nb_(0.99)O₁₄ 0 0.99 0 0.99 Example A-10Li_(2.1)Na_(1.99)Ti_(5.99)Nb_(0.01)O₁₄ 0.1 0.01 0 0.01 Example A-11Li_(2.5)Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄ 0.5 0.5 0 0.5 Example A-12Li₄Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄ 2.0 0.5 0 0.5 Example A-13Li₆Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄ 4.0 0.5 0 0.5 Example A-14Li₂Na_(1.5)Ti_(5.5)Nb_(0.5)O_(13.5) 0 0.5 0 0.5

(Powder X-Ray Diffraction Measurement)

The products of Examples A-1 to A-14 and the products of ComparativeExamples A-1 to A-5 were subjected to the powder X-ray diffractionmeasurement according to the procedure described above.

The following Table 3 shows a crystal plane index corresponding to astrongest diffraction peak L appearing in a range of 17°≦2θ≦18.5°; avalue 2θ_(L) of 2θ of the diffraction peak L; a crystal plane indexcorresponding to a strongest diffraction peak H appearing in a range of18.5°<2θ≦19.5°; a value 2θ_(H) of 2θ of the diffraction peak H; and anintensity ratio I_(L)/I_(H) of these diffraction peaks, which wereobtained from the results of the powder X-ray diffraction measurement ofeach product.

As apparent from the following Table 3, in Comparative Examples A-1a andA-1b, the obtained results of the intensity ratio I_(L)/I_(H) of thediffraction peaks were different from each other, though the targetcompositions are the same. In Comparative Example A-1a, the sinteringwas performed at one time at 1000° C. for a long time withoutconsidering the vaporization amount of Li. On the other hand, inComparative Example A-1b, the synthesis was performed in the same manneras in Example A-1 of the present application. It can be consideredtherefore that if the sintering condition or the feed amount of thelithium starting materials is different, the crystallite growingcondition is also different.

On the other hand, the results of the powder X-ray diffraction wereanalyzed according to a Rietveld method. As a result, it was found thatthe products obtained in Examples A-1 to A-14 were orthorhombic typecompounds having the space group Fmmm symmetry shown in FIG. 2. Crystalphases and space groups of the products are shown in Table 3 altogether.

Next, according to the procedures described above, the amount ofvacancies was obtained from the site occupancy ratio of the Na sites. Asa specific example, the product of Example A-5 is explained. Asdescribed above, the product of Example A-5 is an orthorhombic crystalhaving the space group Fmmm. The sites occupied by Na in the crystalstructure are represented as the 8g site and the 8i site by Wyckoffnotation in the International Tables. Rietveld analysis was performedwhile changing the occupancy ratio g of the Na sites. The result is thatthe fitting parameter S_(vacant) when the the occupancy ratio g is lowerthan 1.0, that is, lower than 100% is smaller than the fitting parameterS₁₀₀ when the occupancy ratio g is 1.0, that is, 100%. From the result,it was confirmed that vacancies exist in the product of Example A-5.Furthermore, the analysis shows that the ratio of vacancies in the Nasites for the product of Example A-5 calculated by the proceduredescribed above by (1−g)×100 was about 25%.

The crystal phase, the space group and the results of determination ofexistence or non-existence of vacancies obtained from occupancy ratio ofthe Na sites of each of products are summarized in Table 3 below.

TABLE 3 Intensity Diffraction Diffraction Ratio of Peak L Line HDiffraction Ratio of Space Plane 2θ/ Plane 2θ/ Peaks Vacancies A seriesComposition Crystal Phase Group Index deg Index deg I_(L)/I_(H) in NaSites Comparative Li₂Na₂Ti₆O₁₄ Orthorhombic Fmmm (111) 18.14 (202) 19.093.06 0 Example A-1a Comparative Li₂Na₂Ti₆O₁₄ Orthorhombic Fmmm (111)18.15 (202) 19.13 2.20 0 Example A-1b Comparative Li_(2.1)Na_(1.9)Ti₆O₁₄Orthorhombic Fmmm (111) 18.16 (202) 19.14 2.21 0 Example A-2 ComparativeLi₂Na₂Ti_(5.9)Nb_(0.1)O₁₄ Orthorhombic Fmmm (111) 18.16 (202) 19.14 2.230 Example A-3 Comparative Li₂MgTi₆O₁₄ Orthorhombic Cmca (021) 18.35(220) 19.34 0.52 — Example A-4 Comparative Li₂BaTi_(5.9)Al_(0.1)O₁₄Orthorhombic Cmca (021) 17.58 (220) 19.28 0.43 — Example A-5 Example A-1Li₂Na_(1.99)Ti_(5.99)Nb_(0.01)O₁₄ Orthorhombic Fmmm (111) 18.16 (202)19.15 2.25  0.5% Example A-2 Li₂Na_(1.95)Ti_(5.95)Nb_(0.05)O₁₄Orthorhombic Fmmm (111) 18.17 (202) 19.16 2.29 2.48% Example A-3Li₂Na_(1.9)Ti_(5.9)Nb_(0.1)O₁₄ Orthorhombic Fmmm (111) 18.17 (202) 19.172.40  4.8% Example A-4 Li₂Na_(1.75)Ti_(5.75)Nb_(0.25)O₁₄ OrthorhombicFmmm (111) 18.17 (202) 19.16 2.43 12.1% Example A-5Li₂Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄ Orthorhombic Fmmm (111) 18.15 (202) 19.142.55 24.8% Example A-6 Li₂Na_(1.25)Ti_(5.25)Nb_(0.75)O₁₄ OrthorhombicFmmm (111) 18.10 (202) 19.11 2.75 37.2% Example A-7Li₂Na_(1.1)Ti_(5.1)Nb_(0.9)O₁₄ Orthorhombic Fmmm (111) 18.11 (202) 19.102.83 45.3% Example A-8 Li₂Na_(1.05)Ti_(5.05)Nb_(0.95)O₁₄ OrthorhombicFmmm (111) 18.12 (202) 19.12 3.21 47.6% Example A-9Li₂Na_(1.01)Ti_(5.01)Nb_(0.99)O₁₄ Orthorhombic Fmmm (111) 18.14 (202)19.14 3.50 49.8% Example A-10 Li_(2.1)Na_(1.99)Ti_(5.99)Nb_(0.01)O₁₄Orthorhombic Fmmm (111) 18.13 (202) 19.14 2.27 0.48% Example A-11Li_(2.5)Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄ Orthorhombic Fmmm (111) 18.14 (202)19.16 2.54 24.6% Example A-12 Li₄Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄Orthorhombic Fmmm (111) 18.13 (202) 19.12 2.35 24.5% Example A-13Li₆Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄ Orthorhombic + Fmmm (111) 18.09 (202)19.06 2.61 24.9% Unknown Phase Example A-14Li₂Na_(1.5)Ti_(5.5)Nb_(0.5)O_(13.5) Orthorhombic Fmmm (111) 18.15 (202)19.14 2.59 24.6%

As typical X-ray charts, X-ray charts in Example A-2, Example A-4,Example A-5, and Example A-6 are shown in FIG. 10.

Example A-15

In Example A-15, a product of Example A-15 was synthesized according tothe following procedures.

First, a part of the product of Example A-5 was immersed into a sucroseaqueous solution having a concentration adjusted to 10% by weight. Then,the sucrose solution was filtered. Then, the filtration residue washeated at 700° C. for 2 hours in a nitrogen atmosphere. The productobtained by the heating was used as the product of Example A-15.

The product of Example A-15 was analyzed by TEM-EDX (transmissionelectron microscopy and energy dispersive X-ray spectroscopy). As aresult, it was found that the surface of the particles of the product ofExample A-5 was coated with carbon.

Example A-16

In Example A-16, a product of Example A-16 was synthesized by coatingthe surface of the product of Example A-5 with lithium titanateLi₄Ti₅O₁₂ using a tumbling fluidized bed granulator according to thefollowing procedures.

Specifically, first, lithium ethoxide and titanium tetraisopropoxidewere mixed in a molar ratio of Li:Ti of 4:5 to prepare a sol-gel liquid.Next, the prepared sol-gel liquid was sprayed to a part of the productof Example A-5 in the tumbling fluidized bed granulator. Thus acomposite in which the sol-gel liquid adhered to the particle surface isobtained. The composite was fired at 600° C. for 2 hours in an airatmosphere, whereby the sol-gel liquid was converted into a spinellithium titanate. The thus obtained product was used as the product ofExample A-16.

The product of Example A-16 was analyzed by TEM-EDX (transmissionelectron microscopy and energy dispersive X-ray spectroscopy), andelectron beam diffraction. As a result, it was found that the surface ofthe particle of the product of Example A-5 was coated with a layer oflithium titanate Li₄Ti₅O₁₂ having spinel type crystal structure.

Example B

In Examples B-1 to B-8, products of Examples B-1 to B-8 were obtained inthe same manner as in Examples A-1 to A-13 except that startingmaterials shown in the following Table 4 were used for obtaining theproducts each of which has a target composition shown in Table 4. Themolar ratios of the starting materials were set to ratios shown in thefollowing Table 4.

TABLE 4 Li Na M1 Ti M2 Source/ Source/ Source/ Source/ Source/ B seriesTarget Composition Amount Amount Amount Amount Amount Example B-1Li₂Na_(1.9)Cs_(0.05)Ti_(5.95)Nb_(0.05)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.95Cs₂CO₃/0.025 TiO₂/5.95 Nb₂O₅/0.025 Example B-2Li₂Na_(1.5)Cs_(0.25)Ti_(5.75)Nb_(0.25)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.75Cs₂CO₃/0.125 TiO₂/5.75 Nb₂O₅/0.125 Example B-3Li₂Na_(1.0)Cs_(0.5)Ti_(5.5)Nb_(0.5)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.5 Cs₂CO₃/0.25TiO₂/5.50 Nb₂O₅/0.25 Example B-4Li₂Na_(0.5)Cs_(0.75)Ti_(5.25)Nb_(0.75)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.25Cs₂CO₃/0.375 TiO₂/5.25 Nb₂O₅/0.375 Example B-5Li₂Na_(0.1)Cs_(0.95)Ti_(5.05)Nb_(0.95)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.05Cs₂CO₃/0.475 TiO₂/5.05 Nb₂O₅/0.475 Example B-6Li₂Na_(0.5)Cs_(1.0)Ti_(5.5)Nb_(0.5)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.25 Cs₂CO₃/0.5TiO₂/5.50 Nb₂O₅/0.25 Example B-7Li₂Na_(0.25)Cs_(1.5)Ti_(5.75)Nb_(0.25)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.125Cs₂CO₃/0.75 TiO₂/5.75 Nb₂O₅/0.125 Example B-8Li₂Na_(0.05)Cs_(1.9)Ti_(5.95)Nb_(0.05)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.025Cs₂CO₃/0.95 TiO₂/5.95 Nb₂O₅/0.025

The products of Examples B-1 to B-8 were subjected to the compositionanalysis and the powder X-ray diffraction measurement in the same manneras in the Example A-series. The results are shown in the following Table5 and Table 6.

TABLE 5 Li_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O₁₄ B series Composition w xy z Example B-1 Li₂Na_(1.9)Cs_(0.05)Ti_(5.95)Nb_(0.05)O₁₄ 0 0.1 0.050.05 Example B-2 Li₂Na_(1.5)Cs_(0.25)Ti_(5.75)Nb_(0.25)O₁₄ 0 0.5 0.250.25 Example B-3 Li₂Na_(1.0)Cs_(0.5)Ti_(5.5)Nb_(0.5)O₁₄ 0 1.0 0.5 0.5Example B-4 Li₂Na_(0.5)Cs_(0.75)Ti_(5.25)Nb_(0.75)O₁₄ 0 1.5 0.75 0.75Example B-5 Li₂Na_(0.1)Cs_(0.95)Ti_(5.05)Nb_(0.95)O₁₄ 0 1.9 0.95 0.95Example B-6 Li₂Na_(0.5)Cs_(1.0)Ti_(5.5)Nb_(0.5)O₁₄ 0 1.5 1.0 0.5 ExampleB-7 Li₂Na_(0.25)Cs_(1.5)Ti_(5.75)Nb_(0.25)O₁₄ 0 1.75 1.5 0.25 ExampleB-8 Li₂Na_(0.05)Cs_(1.9)Ti_(5.95)Nb_(0.05)O₁₄ 0 1.95 1.9 0.05

TABLE 6 Intensity Diffraction Diffraction Ratio of Peak L Peak HDiffraction Ratio of Space Plane 2θ/ Plane 2θ/ Peaks Vacancies B seriesComposition Crystal Phase Group Index deg Index deg I_(L)/I_(H) in NaSites Example B-1 Li₂Na_(1.9)Cs_(0.05)Ti_(5.95)Nb_(0.05)O₁₄ OrthorhombicFmmm (111) 18.13 (202) 19.12 2.27 2.45% Example B-2Li₂Na_(1.5)Cs_(0.25)Ti_(5.75)Nb_(0.25)O₁₄ Orthorhombic Fmmm (111) 18.09(202) 19.08 2.35 11.9% Example B-3Li₂Na_(1.0)Cs_(0.5)Ti_(5.5)Nb_(0.5)O₁₄ Orthorhombic Fmmm (111) 18.01(202) 19.00 2.51 24.9% Example B-4Li₂Na_(0.5)Cs_(0.75)Ti_(5.25)Nb_(0.75)O₁₄ Orthorhombic Fmmm (111) 17.98(202) 18.99 2.55 37.5% Example B-5Li₂Na_(0.1)Cs_(0.95)Ti_(5.05)Nb_(0.95)O₁₄ Orthorhombic Fmmm (111) 17.95(202) 18.94 2.64 47.4% Example B-6Li₂Na_(0.5)Cs_(1.0)Ti_(5.5)Nb_(0.5)O₁₄ Orthorhombic Fmmm (111) 17.93(202) 18.92 2.83 24.8% Example B-7Li₂Na_(0.25)Cs_(1.5)Ti_(5.75)Nb_(0.25)O₁₄ Orthorhombic Fmmm (111) 17.89(202) 18.88 2.78 12.1% Example B-8Li₂Na_(0.05)Cs_(1.9)Ti_(5.95)Nb_(0.05)O₁₄ Orthorhombic Fmmm (111) 17.86(202) 18.86 2.89 2.51%

Example C

In Examples C-1 to C-10, products of Example C-1 to C-10 were obtainedin the same manner as in Examples A-1 to A-12 except that startingmaterials shown in the following Table 7 were used for obtaining theproducts each of which has a target composition shown in Table 7. Themolar ratios of the starting materials were set to ratios shown in thefollowing Table 7.

Comparative Example C

In Comparative Examples C-1 and C-2, products of Comparative ExamplesC-1 and C-2 were obtained in a synthesis manner described in Jpn. Pat.Appln. KOKAI Publication No. 2014-103032, for obtaining the productseach of which has a target composition shown in the following Table 7.The molar ratios of the starting materials were set to ratios shown inthe following Table 7.

TABLE 7 Li Na M1 Ti M2 Source/ Source/ Source/ Source/ Source/ C seriesTarget Composition Amount Amount Amount Amount Amount ComparativeLi₂NaKTi₆O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.5 K₂CO₃/0.5 TiO₂/6.00 — Example C-1Comparative Li₂Na_(1.15)K_(0.6)Rb_(0.25)Ti₆O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.575K₂CO₃/0.3 TiO₂/6.00 — Example C-2 Rb₂CO₃/0.125 Example C-1Li₂Na_(1.9)K_(0.05)Ti_(5.95)Nb_(0.05)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.95K₂CO₃/0.025 TiO₂/5.95 Nb₂O₅/0.025 Example C-2Li₂Na_(1.5)K_(0.25)Ti_(5.75)Nb_(0.25)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.75K₂CO₃/0.125 TiO₂/5.75 Nb₂O₅/0.125 Example C-3Li₂Na_(1.0)K_(0.5)Ti_(5.5)Nb_(0.5)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.5 K₂CO₃/0.25TiO₂/5.50 Nb₂O₅/0.25 Example C-4Li₂Na_(0.5)K_(0.75)Ti_(5.25)Nb_(0.75)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.25K₂CO₃/0.375 TiO₂/5.25 Nb₂O₅/0.375 Example C-5Li₂Na_(0.1)K_(0.95)Ti_(5.05)Nb_(0.95)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.05K₂CO₃/0.475 TiO₂/5.05 Nb₂O₅/0.475 Example C-6Li₂Na_(0.5)K_(1.0)Ti_(5.5)Nb_(0.5)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.25 K₂CO₃/0.5TiO₂/5.50 Nb₂O₅/0.25 Example C-7Li₂Na_(0.25)K_(1.5)Ti_(5.75)Nb_(0.25)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.125K₂CO₃/0.75 TiO₂/5.75 Nb₂O₅/0.125 Example C-8Li₂Na_(0.05)K_(1.9)Ti_(5.95)Nb_(0.05)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.025K₂CO₃/0.95 TiO₂/5.95 Nb₂O₅/0.025 Example C-9Li₂Na_(1.95)K_(0.05)Ti_(5.99)Zr_(0.01)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.975K₂CO₃/0.025 TiO₂/5.99 ZrO₂/0.01 Example C-10 Li₂NaKTi_(5.9)Sn_(0.1)O₁₄Li₂CO₃/1.0 Na₂CO₃/0.5 K₂CO₃/0.5 TiO₂/5.9 SnO₂/0.1

The products of Examples C-1 to C-7 and Comparative Examples C-1 and C-2were subjected to the composition analysis and the powder X-raydiffraction measurement in the same manner as in the Example A-series.The results thereof are shown in the following Table 8 and Table 9.

TABLE 8 Li_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O₁₄ C series Composition w xy z Comparative Li₂NaKTi₆O₁₄ 0 1.0 1.0 0 Example C-1 ComparativeLi₂Na_(1.15)K_(0.6)Rb_(0.25)Ti₆O₁₄ 0 0.85 0.85 0 Example C-2 Example C-1Li₂Na_(1.9)K_(0.05)Ti_(5.95)Nb_(0.05)O₁₄ 0 0.1 0.05 0.05 Example C-2Li₂Na_(1.5)K_(0.25)Ti_(5.75)Nb_(0.25)O₁₄ 0 0.5 0.25 0.25 Example C-3Li₂Na_(1.0)K_(0.5)Ti_(5.5)Nb_(0.5)O₁₄ 0 1.0 0.5 0.5 Example C-4Li₂Na_(0.5)K_(0.75)Ti_(5.25)Nb_(0.75)O₁₄ 0 1.5 0.75 0.75 Example C-5Li₂Na_(0.1)K_(0.95)Ti_(5.05)Nb_(0.95)O₁₄ 0 1.9 0.95 0.95 Example C-6Li₂Na_(0.5)K_(1.0)Ti_(5.5)Nb_(0.5)O₁₄ 0 1.5 1.0 0.5 Example C-7Li₂Na_(0.25)K_(1.5)Ti_(5.75)Nb_(0.25)O₁₄ 0 1.75 1.5 0.25 Example C-8Li₂Na_(0.05)K_(1.9)Ti_(5.95)Nb_(0.05)O₁₄ 0 1.95 1.9 0.05 Example C-9Li₂Na_(1.95)K_(0.05)Ti_(5.99)Zr_(0.01)O₁₄ 0 0.05 0.05 0.01 Example C-10Li₂NaKTi_(5.9)Sn_(0.1)O₁₄ 0 1.0 1.0 0.1

TABLE 9 Intensity Diffraction Diffraction Ratio of Peak L Peak HDiffraction Ratio of Space Plane 2θ/ Plane 2θ/ Peaks Vacancies C seriesComposition Crystal Phase Group Index deg Index deg I_(L)/I_(H) in NaSites Comparative Li₂NaKTi₆O₁₄ Orthorhombic Fmmm (111) 18.23 (202) 19.242.20   0% Example C-1 Comparative Li₂Na_(1.15)K_(0.6)Rb_(0.25)Ti₆O₁₄Orthorhombic Fmmm (111) 18.14 (202) 19.15 2.19   0% Example C-2 ExampleC-1 Li₂Na_(1.9)K_(0.05)Ti_(5.95)Nb_(0.05)O₁₄ Orthorhombic Fmmm (111)18.17 (202) 19.16 2.33 2.48% Example C-2Li₂Na_(1.5)K_(0.25)Ti_(5.75)Nb_(0.25)O₁₄ Orthorhombic Fmmm (111) 18.19(202) 19.18 2.41 12.0% Example C-3 Li₂Na_(1.0)K_(0.5)Ti_(5.5)Nb_(0.5)O₁₄Orthorhombic Fmmm (111) 18.20 (202) 19.20 2.50 25.2% Example C-4Li₂Na_(0.5)K_(0.75)Ti_(5.25)Nb_(0.75)O₁₄ Orthorhombic Fmmm (111) 18.22(202) 19.21 2.85 37.4% Example C-5Li₂Na_(0.1)K_(0.95)Ti_(5.05)Nb_(0.95)O₁₄ Orthorhombic Fmmm (111) 18.24(202) 19.23 2.81 47.6% Example C-6 Li₂Na_(0.5)K_(1.0)Ti_(5.5)Nb_(0.5)O₁₄Orthorhombic Fmmm (111) 18.22 (202) 19.22 2.65 25.0% Example C-7Li₂Na_(0.25)K_(1.5)Ti_(5.75)Nb_(0.25)O₁₄ Orthorhombic Fmmm (111) 18.26(202) 19.25 3.01 11.8% Example C-8Li₂Na_(0.05)K_(1.9)Ti_(5.95)Nb_(0.05)O₁₄ Orthorhombic Fmmm (111) 18.27(202) 19.27 2.71 2.50% Example C-9Li₂Na_(1.95)K_(0.05)Ti_(5.99)Zr_(0.01)O₁₄ Orthorhombic Fmmm (111) 18.18(202) 19.17 2.29   0% Example C-10 Li₂NaKTi_(5.9)Sn_(0.1)O₁₄Orthorhombic Fmmm (111) 18.23 (202) 19.23 2.26   0%

Example D

In Examples D-1 to D-18, products of Examples D-1 to D-18 were obtainedin the same manner as in Examples A-1 to A-12 except that startingmaterials shown in the following Table 10 were used for obtaining theproducts each of which has a target composition shown in Table 10. Themolar ratios of the starting materials were set to ratios shown in thefollowing Table 10.

TABLE 10 Li Na M1 Ti M2 Source/ Source/ Source/ Source/ Source/ D seriesTarget Composition Amount Amount Amount Amount Amount Example D-1Li₂Na_(1.9)Ti_(5.8)(Nb_(0.1)Zr_(0.1))O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.95 —TiO₂/5.80 ZrO₂/0.1 Nb₂O₅/0.05 Example D-2Li₂Na_(1.9)Ti_(5.8)(Nb_(0.1)Sn_(0.1))O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.95 —TiO₂/5.80 SnO₂/0.1 Nb₂O₅/0.05 Example D-3Li₂Na_(1.5)Ti_(5.4)(Nb_(0.5)Sn_(0.1))O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.75 —TiO₂/5.40 SnO₂/0.1 Nb₂O₅/0.25 Example D-4 Li₂Na_(1.9)Ti_(5.9)V_(0.1)O₁₄Li₂CO₃/1.0 Na₂CO₃/0.95 — TiO₂/5.90 V₂O₅/0.05 Example D-5Li₂Na_(1.8)Ti_(5.8)(Nb_(0.1)V_(0.1))O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.90 —TiO₂/5.80 V₂O₅/0.05 Nb₂O₅/0.05 Example D-6Li₂Na_(1.9)Ti_(5.9)Ta_(0.1)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.95 — TiO₂/5.90Ta₂O₅/0.05 Example D-7 Li₂Na_(1.99)Ti_(5.99)Ta_(0.01)O₁₄ Li₂CO₃/1.0Na₂CO₃/0.995 — TiO₂/5.99 Ta₂O₅/0.005 Example D-8Li₂Na_(1.9)Ti_(5.9)(Nb_(0.09)Ta_(0.01))O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.95 —TiO₂/5.90 Ta₂O₅/0.005 Nb₂O₅/0.045 Example D-9Li₂Na_(1.5)Ti_(5.5)(Nb_(0.49)Ta_(0.01))O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.75 —TiO₂/5.50 Ta₂O₅/0.005 Nb₂O₅/0.245 Example D-10Li₂Na_(1.5)Ti_(5.5)(Nb_(0.4)Ta_(0.1))O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.75 —TiO₂/5.50 Ta₂O₅/0.05 Nb₂O₅/0.2 Example D-11Li₂Na_(1.25)Ti_(5.75)(Nb_(0.74)Ta_(0.01))O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.625 —TiO₂/5.75 Ta₂O₅/0.005 Nb₂O₅/0.37 Example D-12Li₂Na_(1.8)Ti_(5.9)Mo_(0.1)O₁₄ Li₂CO₃/1.0 Na₂CO₃/0.90 — TiO₂/5.90MoO₃/0.1 Example D-13 Li₂Na_(1.4)Ti_(5.6)(Nb_(0.2)Mo_(0.2))O₁₄Li₂CO₃/1.0 Na₂CO₃/0.70 — TiO₂/5.60 Nb₂O₅/0.1 MoO₃/0.2 Example D-14Li_(2.2)Na_(1.9)Ti_(5.9)Fe_(0.1)O₁₄ Li₂CO₃/1.10 Na₂CO₃/0.95 — TiO₂/5.90Fe₂O₃/0.05 Example D-15 Li_(2.2)Na_(1.5)Ti_(5.5)(Nb_(0.4)Fe_(0.1))O₁₄Li₂CO₃/1.10 Na₂CO₃/0.75 — TiO₂/5.50 Nb₂O₅/0.20 Fe₂O₃/0.05 Example D-16Li_(2.2)Na_(1.9)Ti_(5.9)Co_(0.1)O₁₄ Li₂CO₃/1.10 Na₂CO₃/0.95 — TiO₂/5.90Co₂O₃/0.05 Example D-17 Li_(2.2)Na_(1.9)Ti_(5.9)Mn_(0.1)O₁₄ Li₂CO₃/1.10Na₂CO₃/0.95 — TiO₂/5.90 Mn₂O₃/0.05 Example D-18Li_(2.2)Na_(1.9)Ti_(5.9)Al_(0.1)O₁₄ Li₂CO₃/1.10 Na₂CO₃/0.95 — TiO₂/5.90Al₂O₃/0.05

The products of Examples D-1 to D-18 were subjected to compositionanalysis and powder X-ray diffraction measurement in the same manner asin the Example A-series. The results thereof are shown in the followingTable 11 and Table 12.

TABLE 11 Li_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O₁₄ D series Composition wx y z Example D-1 Li₂Na_(1.9)Ti_(5.8)(Nb_(0.1)Zr_(0.1))O₁₄ 0 0.1 0 0.2Example D-2 Li₂Na_(1.9)Ti_(5.8)(Nb_(0.1)Sn_(0.1))O₁₄ 0 0.1 0 0.2 ExampleD-3 Li₂Na_(1.5)Ti_(5.4)(Nb_(0.5)Sn_(0.1))O₁₄ 0 0.5 0 0.6 Example D-4Li₂Na_(1.9)Ti_(5.9)V_(0.1)O₁₄ 0 0.1 0 0.1 Example D-5Li₂Na_(1.8)Ti_(5.8)(Nb_(0.1)V_(0.1))O₁₄ 0 0.2 0 0.2 Example D-6Li₂Na_(1.9)Ti_(5.9)Ta_(0.1)O₁₄ 0 0.1 0 0.1 Example D-7Li₂Na_(1.99)Ti_(5.99)Ta_(0.01)O₁₄ 0 0.01 0 0.01 Example D-8Li₂Na_(1.9)Ti_(5.9)(Nb_(0.09)Ta_(0.01))O₁₄ 0 0.1 0 0.1 Example D-9Li₂Na_(1.5)Ti_(5.5)(Nb_(0.49)Ta_(0.01))O₁₄ 0 0.5 0 0.5 Example D-10Li₂Na_(1.5)Ti_(5.5)(Nb_(0.4)Ta_(0.1))O₁₄ 0 0.5 0 0.5 Example D-11Li₂Na_(1.25)Ti_(5.75)(Nb_(0.74)Ta_(0.01))O₁₄ 0 0.75 0 0.75 Example D-12Li₂Na_(1.8)Ti_(5.9)Mo_(0.1)O₁₄ 0 0.2 0 0.1 Example D-13Li₂Na_(1.4)Ti_(5.6)(Nb_(0.2)Mo_(0.2))O₁₄ 0 0.6 0 0.4 Example D-14Li_(2.2)Na_(1.9)Ti_(5.9)Fe_(0.1)O₁₄ 0.2 0.1 0 0.1 Example D-15Li_(2.2)Na_(1.5)Ti_(5.5)(Nb_(0.4)Fe_(0.1))O₁₄ 0.2 0.5 0 0.5 Example D-16Li_(2.2)Na_(1.9)Ti_(5.9)Co_(0.1)O₁₄ 0.2 0.1 0 0.1 Example D-17Li_(2.2)Na_(1.9)Ti_(5.9)Mn_(0.1)O₁₄ 0.2 0.1 0 0.1 Example D-18Li_(2.2)Na_(1.9)Ti_(5.9)Al_(0.1)O₁₄ 0.2 0.1 0 0.1

TABLE 12 Intensity Diffraction Diffraction Ratio of Peak L Peak HDiffraction Ratio of Space Plane 2θ/ Plane 2θ/ Peaks Vacancies D seriesComposition Crystal Phase Group Index deg Index deg I_(L)/I_(H) in NaSites Example D-1 Li₂Na_(1.9)Ti_(5.8)(Nb_(0.1)Zr_(0.1))O₁₄ OrthorhombicFmmm (111) 18.16 (202) 19.16 2.41 4.9% Example D-2Li₂Na_(1.9)Ti_(5.8)(Nb_(0.1)Sn_(0.1))O₁₄ Orthorhombic Fmmm (111) 18.16(202) 19.16 2.45 5.0% Example D-3Li₂Na_(1.5)Ti_(5.4)(Nb_(0.5)Sn_(0.1))O₁₄ Orthorhombic Fmmm (111) 18.15(202) 19.14 2.56 25.1%  Example D-4 Li₂Na_(1.9)Ti_(5.9)V_(0.1)O₁₄Orthorhombic Fmmm (111) 18.16 (202) 19.16 2.43 5.1% Example D-5Li₂Na_(1.8)Ti_(5.8)(Nb_(0.1)V_(0.1))O₁₄ Orthorhombic Fmmm (111) 18.16(202) 19.16 2.42 9.9% Example D-6 Li₂Na_(1.9)Ti_(5.9)Ta_(0.1)O₁₄Orthorhombic Fmmm (111) 18.17 (202) 19.17 2.46 5.0% Example D-7Li₂Na_(1.99)Ti_(5.99)Ta_(0.01)O₁₄ Orthorhombic Fmmm (111) 18.16 (202)19.15 2.28 0.50%  Example D-8 Li₂Na_(1.9)Ti_(5.9)(Nb_(0.09)Ta_(0.01))O₁₄Orthorhombic Fmmm (111) 18.16 (202) 19.15 2.42 4.9% Example D-9Li₂Na_(1.5)Ti_(5.5)(Nb_(0.49)Ta_(0.01))O₁₄ Orthorhombic Fmmm (111) 18.15(202) 19.14 2.53 25.0%  Example D-10Li₂Na_(1.5)Ti_(5.5)(Nb_(0.4)Ta_(0.1))O₁₄ Orthorhombic Fmmm (111) 18.15(202) 19.14 2.55 24.9%  Example D-11Li₂Na_(1.25)Ti_(5.75)(Nb_(0.74)Ta_(0.01))O₁₄ Orthorhombic Fmmm (111)18.10 (202) 19.11 2.77 37.6%  Example D-12Li₂Na_(1.8)Ti_(5.9)Mo_(0.1)O₁₄ Orthorhombic Fmmm (111) 18.17 (202) 19.172.50 10.1%  Example D-13 Li₂Na_(1.4)Ti_(5.6)(Nb_(0.2)Mo_(0.2))O₁₄Orthorhombic Fmmm (111) 18.18 (202) 19.18 2.52 29.8%  Example D-14Li_(2.2)Na_(1.9)Ti_(5.9)Fe_(0.1)O₁₄ Orthorhombic Fmmm (111) 18.17 (202)19.17 2.55 4.9% Example D-15Li_(2.2)Na_(1.5)Ti_(5.5)(Nb_(0.4)Fe_(0.1))O₁₄ Orthorhombic Fmmm (111)18.15 (202) 19.14 2.58 24.8%  Example D-16Li_(2.2)Na_(1.9)Ti_(5.9)Co_(0.1)O₁₄ Orthorhombic Fmmm (111) 18.16 (202)19.17 2.57 4.8% Example D-17 Li_(2.2)Na_(1.9)Ti_(5.9)Mn_(0.1)O₁₄Orthorhombic Fmmm (111) 18.17 (202) 19.17 2.56 4.9% Example D-18Li_(2.2)Na_(1.9)Ti_(5.9)Al_(0.1)O₁₄ Orthorhombic Fmmm (111) 18.16 (202)19.16 2.53 4.9%

(Electrochemical Measurement)

Each of the products obtained in Examples and Comparative Examplesdescribed above was subjected to an electrochemical measurementaccording to the following procedures. The following explanation is madeusing the product of Example A-1 as an example, and the electrochemicalmeasurement of the products of other Examples and Comparative Exampleswere performed in the same manner as in that of the product of ExampleA-1.

First, the product particles of Example A-1 were ground to obtain aground product having an average particle size of 5 μm or less. Next,acetylene black, as a conductive agent, was mixed with the activematerial in a proportion of 10 parts by mass relative to the activematerial to obtain a mixture. Next, the mixture was dispersed in NMP(N-methyl-2-pyrrolidone) to obtain a dispersion. Polyvinylidene fluoride(PVdF), as a binder, was mixed with the dispersion in a proportion of 10parts by mass relative to the product of Example to obtain an electrodeslurry. A current collector, formed of an aluminum foil, was coated withthe slurry using a blade. This was dried at 130° C. for 12 hours undervacuum, and then rolled so that the density of an electrode layer(excluding a current collector) was 2.2 g/cm³ to obtain an electrode.

Using this electrode, a metal lithium foil as a counter electrode andnonaqueous electrolyte, an electrochemical measurement cell of Examplewas produced. As a nonaqueous electrolyte, a mixture in which lithiumhexafluorophosphate (LiPF₆) was dissolved in a concentration of 1 M in amixed solvent of ethylene carbonate and diethyl carbonate (volume ratioof 1:1) was used.

The electrochemical measurement cell of Example A-1 was subjected to acharge-and-discharge test at room temperature. The charge-and-dischargetest was performed within a potential range of 1.0 V to 3.0 V withreference to the metal lithium electrode at a charge-and-dischargecurrent value of 0.2 C (hourly discharge rate). In this test, a first Liinserion amount was defined as an initial charge capacity, and a firstLi extraction amount was defined as an initial discharge capacity. Atthis time, a value obtained by dividing an initial discharge capacity bythe initial charge capacity, and multiplying the obtained value by 100(initial discharge capacity/initial charge capacity×100) was defined asan initial charge-and-discharge efficiency.

Next, in order to confirm whether or not the product of Example A-1 canbe stably charged and discharged, the electrochemical measurement cellof Example A-1 was repeatedly subjected to 50 cycles of charge anddischarge. One cycle consisted of one charge and one discharge. Thecharge and discharge were performed at room temperature within apotential range of 1.0 V to 3.0 V with reference to the metal lithiumelectrode at a current value of 1 C (hourly discharge rate).

In order to confirm the discharge capacity retention ratio after 50cycles, the electrochemical measurement cell of Example was charged anddischarged again at 0.2 C (hourly discharge rate), and the capacityretention ratio was calculated with the initial discharge capacitydefined as 100%.

In addition, the discharge capacity at 0.2 C and the discharge capacityat 10.0 C of the electrochemical measurement cell of Example A-1 weremeasured. The discharge rate was calculated as the barometer of the rateperformance by dividing the discharge capacity at 10 C obtained by themeasurement by the capacity at 0.2 C similarly obtained by themeasurement.

[Charge-And-Discharge Curve]

FIG. 11 shows initial charge and discharge curves obtained by theelectrochemical measurement of the electrochemical measurement cells ofExamples A-4, A-5, A-6 and A-9 and a electrochemical measurement cell ofComparative Example A-1b. In FIG. 11, the curves of long dashed andshort dashes line having symbol (1) show a potential change of theelectrode containing the orthorhombic crystal composite oxide of ExampleA-4. the solid line curves having symbol (2) show a potential changecontaining the orthorhombic crystal composite oxide of Example A-5. Thebroken line curves having symbol (3) show a potential change of theelectrode containing the orthorhombic crystal composite oxide of ExampleA-6. The solid line curves having symbol (4) show a potential change ofthe electrode containing the orthorhombic crystal composite oxide ofExample A-9. The dotted line curves having symbol (5) show a potentialchange of the electrode containing the orthorhombic crystal compositeoxide of Comparative Example A-1b.

As apparent from FIG. 11, in a potential of the electrochemicalmeasurement cell within a range of 1.0 V (vs. Li/Li⁺) to 2.0 V (vs.Li/Li⁺) as the effective potential range of the negative electrode, thecharge-and-discharge curve of Comparative Example A-1b had, within awide range of the capacity, potential flat parts in which the variationin the potential accompanied with a change in the capacity is small. Theproduct of Comparative Example A-1b exhibiting such charge-and-dischargecurve is not practically preferable, because it is difficult tocomprehend the correlation between the charging capacity and the batteryvoltage, as described above. Furthermore, the electrode of ComparativeExample A-1b has a small capacity, i.e., about 90 mAh/g.

On the contrary, as shown in FIG. 11, each of the charge-and-dischargecurves of Examples A-4, A-5, A-6, and A-9 has, within a range of 1.0 V(vs. Li/Li⁺) to 2.0 V (vs. Li/Li⁺), a continuous potential-gradientexhibiting a large variation in the potential with the change of chargedor discharged capacity. As for a rechargeable battery, a state-of-charge(residual capacity) of the battery can be estimated by examining abattery voltage. The continuous potential gradient, which can beexhibited by the products of Examples A-4, A-5, A-6, and A-9, is usefulto control the charge-and-discharge of the battery. In addition, asapparent from FIG. 11, the electrode capacities in Examples A-4, A-5,A-6, and A-9 are higher than that in Comparative Example A-1b. Theproducts of Examples A-4, A-5, A-6, and A-9 accordingly can provide abattery exhibiting a high energy density.

On the other hand, in the charge-and-discharge curves in Examples A-4,A-5, A-6, and A-9, an electrode potential to metal Li at SOC=50% (astate in which a half of the charge capacity is charged) varies within arange of 1.43 V to 1.30 V. It is found from this result and thecompositions shown in Table 2 that a battery voltage can be arbitrarilycontrolled, depending on the application of the battery, by changing thevalue of the subscript x in the general formula ofLi_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O_(14+δ) for the composite oxide.For example, when the battery is used for a battery module forautomobiles, whose operating voltage range is decided, a desired batteryvoltage can be obtained by changing a negative electrode potentialaccording to the positive electrode to be combined, as shown inExamples.

The initial charge-and-discharge curves of the electrochemicalmeasurement cells of Examples A-1 to A-3, A-7, A-8, A-10 to A-16, B-1 toB-8, C-1 to C-10, and D-1 to D-18, which are not shown, as in ExamplesA-4 to 6, and A-9, had, in the battery voltage of each of theelectrochemical measurement cell within a range of 1.0 V to 2.0 V, avariation in the potential accompanied with a change in the capacityduring the charge-and-discharge larger than that in Comparative ExampleA-1b, and exhibited a continuous potential gradient corresponding to thecharged or discharged capacity. In addition, the electrode capacities inthese Examples were higher than that in Comparative Example A-1b.

Table 13 to Table 16 below show an initial discharge capacity (mAh/g),an initial charge-and-discharge efficiency (%), a 10 C/0.2 C dischargecapacity ratio (%), a capacity retension ratio after 50 cycles, apotential (V vs. Li/Li⁺) in a half charge state (50% state-of-charge=SOC50% when a full charge is defined as 100%), and a difference inpotential ΔV (mV) between SOC 20-80%, of each the electrochemicalmeasurement cells of Examples A series to D series, Comparative ExampleA series, and Comparative Examples C series.

Here, the potential in SOC 50% refers to an electrode potential based onmetal lithium in the half state-of-charge and in an open circuit state(the potential is defined as a potential of the cell in the state inwhich the cell has been kept in the open circuit state for one hourafter charging the cell at 0.2 C from the completely discharged state(Li extracted state) to 50% of the capacity (Li insertion)).

The difference in potential ΔV between SOC 20-80% refers to a differencein potential between an electrode potential (vs. metal lithium) at 20%of 0.2 C discharge capacity and an electrode potential (vs. metallithium) at 80%.

The calculation method of the difference in potential is as follows:FIG. 12 shows a discharge (Li extraction) curve ofLi₂Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄ as one example. First, Li is inserted toan electrode containing a composite oxide to be measured at a chargerate of 0.2 C, then the electrode is subjected to a constant-voltagecharge at 1.0 V (vs. metal lithium potential) for 5 hours, and aone-hour suspension is taken (CC-CV charge). Next, the electrode isdischarged (Li extraction) at 0.2 C up to 2.0 V (vs. metal lithium).Thus, the discharge curve as shown in FIG. 12 can be obtained. Dischargeof the total capacity at this time is defined as 100%, and a differencebetween a potential (vs. metal lithium) at capacity C₂₀, correspondingto 20%, and a potential (vs. metal lithium) at capacity C₈₀,corresponding to 80%, is obtained from the discharge curve obtained asabove. In FIG. 12, the potential is 1.445 V (vs. Li/Li⁺) at SOC 80% andthe potential is 1.264 V (vs. Li/Li⁺) at SOC 20%. The differencethereof, i.e., the difference in potential ΔV is, accordingly, 181 mV.The higher the numerical value is, the larger the electrode potentialwith the change of the capacity during charge and discharge is. In anelectrode this value of which is high, the correlation between thecharged or discharged capacity and the battery voltage can be easilycomprehended, and it can be presumed that the charge-and-discharge canbe easily managed in such an electrode.

TABLE 13 Initial 10 C/0.2 C Capacity Difference Initial Charge-and-Discharge Retention in potential Discharge Discharge Capacity Ratioafter Potential between SOC20% Capacity Efficiency Ratio 50 Cycles inSOC50% and SOC80% ΔV A series Composition (mAh/g) (%) (%) (%) (V vs.Li⁺/Li) (mV) Comparative Li₂Na₂Ti₆O₁₄ 90.8 92.0 89.8 90.5 1.28 36Example A-1a Comparative Li₂Na₂Ti₆O₁₄ 90.7 92.2 90.1 90.7 1.28 35Example A-1b Comparative Li_(2.1)Na_(1.9)Ti₆O₁₄ 91.5 90.9 89.3 90.1 1.2736 Example A-2 Comparative Li₂Na₂Ti_(5.9)Nb_(0.1)O₁₄ 91.6 92.3 90.9 91.31.28 38 Example A-3 Comparative Li₂MgTi₆O₁₄ 96.1 91.8 86.5 87.3 1.42 18Example A-4 Comparative Li₂BaTi_(5.9)Al_(0.1)O₁₄ 107.3 90.9 84.3 90.11.43 16 Example A-5 Example A-1 Li₂Na_(1.99)Ti_(5.99)Nb_(0.01)O₁₄ 92.092.1 89.9 91.5 1.28 40 Example A-2 Li₂Na_(1.95)Ti_(5.95)Nb_(0.05)O₁₄92.8 92.2 91.5 93.0 1.28 76 Example A-3 Li₂Na_(1.9)Ti_(5.9)Nb_(0.1)O₁₄101.7 92.3 91.4 92.8 1.29 118 Example A-4Li₂Na_(1.75)Ti_(5.75)Nb_(0.25)O₁₄ 115.9 92.5 92.7 93.8 1.30 129 ExampleA-5 Li₂Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄ 131.5 93.5 92.9 93.6 1.34 181 ExampleA-6 Li₂Na_(1.25)Ti_(5.25)Nb_(0.75)O₁₄ 129.8 93.1 92.8 93.3 1.39 193Example A-7 Li₂Na_(1.1)Ti_(5.1)Nb_(0.9)O₁₄ 128.5 92.8 91.3 92.8 1.41 183Example A-8 Li₂Na_(1.05)Ti_(5.05)Nb_(0.95)O₁₄ 127.9 92.9 92.5 93.5 1.41179 Example A-9 Li₂Na_(1.01)Ti_(5.01)Nb_(0.99)O₁₄ 122.3 92.7 92.1 93.61.43 180 Example A-10 Li_(2.1)Na_(1.99)Ti_(5.99)Nb_(0.01)O₁₄ 91.8 91.793.6 93.4 1.28 43 Example A-11 Li_(2.5)Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄ 128.993.9 93.2 92.9 1.33 181 Example A-12 Li₄Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄109.0 93.4 92.6 93.9 1.32 178 Example A-13Li₆Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄ 92.4 92.6 92.8 92.2 1.31 165 Example A-14Li₂Na_(1.5)Ti_(5.5)Nb_(0.5)O_(13.5) 132.4 93.9 95.7 94.8 1.35 182Example A-15 Li₂Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄ 133.3 94.1 96.0 94.9 1.34181 Example A-16 Li₂Na_(1.5)Ti_(5.5)Nb_(0.5)O₁₄ 131.7 94.0 95.5 95.11.34 183

TABLE 14 Initial 10 C/0.2 C Capacity Difference Initial Charge-and-Discharge Retention in potential Discharge Discharge Capacity Ratioafter Potential between SOC20% Capacity Efficiency Ratio 50 Cycles inSOC50% and SOC80% ΔV B series Composition (mAh/g) (%) (%) (%) (V vs.Li⁺/Li) (mV) Example B-1 Li₂Na_(1.9)Cs_(0.05)Ti_(5.95)Nb_(0.05)O₁₄ 93.192.6 92.0 93.4 1.28 81 Example B-2Li₂Na_(1.5)Cs_(0.25)Ti_(5.75)Nb_(0.25)O₁₄ 116.7 92.3 93.1 93.6 1.31 131Example B-3 Li₂Na_(1.0)Cs_(0.5)Ti_(5.5)Nb_(0.5)O₁₄ 121.9 92.5 92.8 93.11.42 178 Example B-4 Li₂Na_(0.5)Cs_(0.75)Ti_(5.25)Nb_(0.75)O₁₄ 128.493.3 93.2 93.8 1.42 186 Example B-5Li₂Na_(0.1)Cs_(0.95)Ti_(5.05)Nb_(0.95)O₁₄ 126.6 92.7 92.9 93.1 1.42 165Example B-6 Li₂Na_(0.5)Cs_(1.0)Ti_(5.5)Nb_(0.5)O₁₄ 120.3 92.2 92.3 93.81.42 155 Example B-7 Li₂Na_(0.25)Cs_(1.5)Ti_(5.75)Nb_(0.25)O₁₄ 115.992.1 92.6 94.2 1.30 128 Example B-8Li₂Na_(0.05)Cs_(1.9)Ti_(5.95)Nb_(0.05)O₁₄ 92.5 91.8 91.9 93.7 1.25 92

TABLE 15 Initial 10 C/0.2 C Capacity Difference Initial Charge-and-Discharge Retention in potential Discharge Discharge Capacity Ratioafter Potential between SOC20% Capacity Efficiency Ratio 50 Cycles inSOC50% and SOC80% ΔV C series Composition (mAh/g) (%) (%) (%) (V vs.Li⁺/Li) (mv) Comparative Li₂NaKTi₆O₁₄ 86.8 92.3 88.8 89.5 1.26 38Example C-1 Comparative Li₂Na_(1.15)K_(0.6)Rb_(0.25)Ti₆O₁₄ 83.5 92.090.4 90.1 1.26 39 Example C-2 Example C-1Li₂Na_(1.9)K_(0.05)Ti_(5.95)Nb_(0.05)O₁₄ 93.1 92.6 91.3 92.7 1.28 78Example C-2 Li₂Na_(1.5)K_(0.25)Ti_(5.75)Nb_(0.25)O₁₄ 116.4 92.3 92.493.6 1.30 129 Example C-3 Li₂Na_(1.0)K_(0.5)Ti_(5.5)Nb_(0.5)O₁₄ 130.993.4 92.6 93.9 1.34 181 Example C-4Li₂Na_(0.5)K_(0.75)Ti_(5.25)Nb_(0.75)O₁₄ 129.5 93.0 92.8 93.6 1.39 195Example C-5 Li₂Na_(0.1)K_(0.95)Ti_(5.05)Nb_(0.95)O₁₄ 127.7 92.9 92.393.1 1.41 176 Example C-6 Li₂Na_(0.5)K_(1.0)Ti_(5.5)Nb_(0.5)O₁₄ 129.293.1 92.5 93.6 1.35 178 Example C-7Li₂Na_(0.25)K_(1.5)Ti_(5.75)Nb_(0.25)O₁₄ 115.3 92.5 92.8 93.3 1.32 125Example C-8 Li₂Na_(0.05)K_(1.9)Ti_(5.95)Nb_(0.05)O₁₄ 92.5 92.2 91.9 93.41.30 73 Example C-9 Li₂Na_(1.95)K_(0.05)Ti_(5.99)Zr_(0.01)O₁₄ 92.1 92.390.5 92.8 1.26 42 Example C-10 Li₂NaKTi_(5.9)Sn_(0.1)O₁₄ 92.0 92.7 91.792.2 1.26 45

TABLE 16 Initial 10 C/0.2 C Capacity Difference Initial Charge-and-Discharge Retention in potential Discharge Discharge Capacity Ratioafter Potential between SOC20% Capacity Efficiency Ratio 50 Cycles inSOC50% and SOC80% ΔV D series Composition (mAh/g) (%) (%) (%) (V vs.Li⁺/Li) (mV) Example D-1 Li₂Na_(1.9)Ti_(5.8)(Nb_(0.1)Zr_(0.1))O₁₄ 100.592.4 91.8 93.2 1.29 119 Example D-2Li₂Na_(1.9)Ti_(5.8)(Nb_(0.1)Sn_(0.1))O₁₄ 99.7 92.1 92.0 92.9 1.29 116Example D-3 Li₂Na_(1.5)Ti_(5.4)(Nb_(0.5)Sn_(0.1))O₁₄ 131.4 93.8 93.393.9 1.34 180 Example D-4 Li₂Na_(1.9)Ti_(5.9)V_(0.1)O₁₄ 101.8 92.6 92.593.5 1.29 117 Example D-5 Li₂Na_(1.8)Ti_(5.8)(Nb_(0.1)V_(0.1))O₁₄ 102.593.5 93.4 93.4 1.29 118 Example D-6 Li₂Na_(1.9)Ti_(5.9)Ta_(0.1)O₁₄ 101.992.1 91.6 92.5 1.29 115 Example D-7 Li₂Na_(1.99)Ti_(5.99)Ta_(0.01)O₁₄92.2 92.3 90.2 91.8 1.28 46 Example D-8Li₂Na_(1.9)Ti_(5.9)(Nb_(0.09)Ta_(0.01))O₁₄ 102.3 92.2 91.7 92.6 1.29 116Example D-9 Li₂Na_(1.5)Ti_(5.5)(Nb_(0.49)Ta_(0.01))O₁₄ 133.5 93.8 93.194.3 1.34 182 Example D-10 Li₂Na_(1.5)Ti_(5.5)(Nb_(0.4)Ta_(0.1))O₁₄129.4 93.7 92.8 93.6 1.34 178 Example D-11Li₂Na_(1.25)Ti_(5.75)(Nb_(0.74)Ta_(0.01))O₁₄ 130.1 93.5 93.0 93.9 1.39200 Example D-12 Li₂Na_(1.8)Ti_(5.9)Mo_(0.1)O₁₄ 100.5 92.1 92.3 92.81.29 111 Example D-13 Li₂Na_(1.4)Ti_(5.6)(Nb_(0.2)Mo_(0.2))O₁₄ 130.692.4 93.3 93.0 1.34 179 Example D-14 Li_(2.2)Na_(1.9)Ti_(5.9)Fe_(0.1)O₁₄99.3 92.0 92.7 92.5 1.28 108 Example D-15Li_(2.2)Na_(1.5)Ti_(5.5)(Nb_(0.4)Fe_(0.1))O₁₄ 135.5 93.7 93.3 94.1 1.34180 Example D-16 Li_(2.2)Na_(1.9)Ti_(5.9)Co_(0.1)O₁₄ 98.3 92.3 92.9 93.01.28 109 Example D-17 Li_(2.2)Na_(1.9)Ti_(5.9)Mn_(0.1)O₁₄ 99.0 92.1 92.792.7 1.28 106 Example D-18 Li_(2.2)Na_(1.9)Ti_(5.9)Al_(0.1)O₁₄ 97.7 92.192.9 92.4 1.28 108

Example E

In Example E, a nonaqueous electrolyte battery was produced according tothe following procedures.

(Production of Negative Electrode)

First, particles of the product of Example A-5 were ground so that theaverage particle size was 5 μm or less to obtain a ground product. Next,acetylene black, as a conductive agent, was mixed with the activematerial in an amount of 6 parts by mass relative to the active materialto obtain a mixture. Next, the mixture was dispersed in NMP(N-methyl-2-pyrrolidone) to obtain a dispersion. Polyvinylidene fluoride(PVdF), as a binder, was mixed with the dispersion in an amount of 10parts by mass relative to the product of Example A-5 to prepare anegative electrode slurry. A current collector, formed of aluminum foil,was coated with the slurry using a blade. After the obtained product wasdried at 130° C. for 12 hours in vacuum, it was rolled so that a densityof the electrode layer (excluding a current collector) was 2.2 g/cm³ toobtain a negative electrode.

(Production of Positive Electrode)

With a commercially available spinel lithium manganese oxide (LiMn₂O₄)was mixed 5 parts by weight of acetylene black as a conduction aid toobtain a mixture. Next, the mixture was dispersed in NMP to obtain adispersion. To the dispersion was mixed with PVdF, as a binder, in anamount of 5 parts by weight relative to the lithium manganese oxide toprepare a positive electrode slurry. A current collector, formed of analuminum foil, was coated with the slurry using a blade. After theobtained product was dried at 130° C. for 12 hours in vacuum, it wasrolled so that a density of the electrode layer (excluding a currentcollector) was 2.1 g/cm³, to obtain a positive electrode.

(Production of Electrode Group)

The positive electrode and the negative electrode produced as descrivedabove were laminated with a polyethylene separator sandwiched betweenthem to obtain a laminate. Next, this laminate was coiled and pressed toobtain a flat-shaped coiled electrode group. A positive electrodeterminal and a negative electrode terminal were connected to thiselectrode group.

(Preparation of Nonaqueous Electrolyte)

As a mixed solvent, a mixed solvent of ethylene carbonate and diethylcarbonate (volume ratio of 1:1) was provided. Lithiumhexafluorophosphate (LiPF₆) was dissolved in this solvent in aconcentration of 1 M. Thus, a nonaqueous electrolyte was prepared.

(Assembly of Nonaqueous Electrolyte Battery)

Using the electrode group and the nonaqueous electrolyte produced asdescribed above, a nonaqueous electrolyte battery of Example E wasfabricated.

(Charge-And-Discharge Test)

The nonaqueous electrolyte battery of Example E was subjected to acharge-and-discharge test at room temperature. The charge-and-dischargetest was performed at a charge-and-discharge current value of 0.2 C (atime discharge rate) within a potential range of 1.8 V to 3.1 V as thebattery voltage.

FIG. 13 shows a charge-and-discharge curve of the nonaqueous electrolytebattery of Example E. As apparent from FIG. 13, in the nonaqueouselectrolyte battery of Example E, the voltage smoothly varies within avoltage range of 2.3 V to 3.0 V, that is, a nonaqueous electrolytebattery in which the voltage smoothly varies within a voltage range of2.3 V to 3.0 V could be obtained by using the product of Example A-5.When five of the nonaqueous electrolyte batteries were connected to eachother in series, a higher operating voltage than that obtained in a caseusing a spinel lithium titanate (Li₄Ti₅O₁₂) as the negative electrode,i.e., 15.1 V to 11.5 V, was obtained, from which a battery pack having avoltage compatible with a 12 V lead storage battery for automobiles canbe fabricated.

Example F

In Example F, battery modules of Examples F-1 to F-4 were producedaccording to the following procedures.

Example F-1

In Example F-1, five nonaqueous electrolyte batteries of Example F-1were produced in the same procedures as described in Example E exceptthat the particles of the product of Example A-4 were used instead ofthe particles of the product of Example A-5 when the negative electrodewas produced.

Next, the five nonaqueous electrolyte batteries produced wereelectrically connected to each other in series. The thus obtainedbattery module was used as the battery module of Example F-1.

Example F-2 to F-4

In Examples F-2 to F-4, battery modules of Examples F-2 to F2-4 wereproduced in the same procedures as in Example F-1 except that thenonaqueous electrolyte battery of each of Examples F-2 to F-4 producedin the following procedures was used.

In Example F-2, five nonaqueous electrolyte batteries each of which wasthe same as the nonaqueous electrolyte battery of Example E wereproduced in the same procedures as described in Example E. They wereused as the nonaqueous electrolyte batteries of Example F-2.

In Example F-3, five nonaqueous electrolyte batteries of Example F-3were produced in the same procedures as described in Example E exceptthat the particles of the product of Example A-6 were used instead ofthe particles of the product of Example A-5 when the negative electrodewas produced.

In Example F-4, five nonaqueous electrolyte batteries of Example F-4were produced in the same procedures as described in Example E exceptthat the particles of the product of Example A-9 were used instead ofthe particles of the product of Example A-5 when the negative electrodewas produced.

(Charge-And-Discharge Test)

The battery modules of Examples F-1 to F-4 were subjected to acharge-and-discharge test at room temperature. The charge-and-dischargetest was performed at a charge-and-discharge current value of 0.2 C (atime discharge rate) within a potential range of 9.0 V to 15.5 V as thevoltage of the battery module.

FIG. 14 shows discharge curves of the battery modules of Examples F-1 toF-4. In FIG. 14, the curve of long dashed and short dashed line havingsymbol (1) shows a discharge curve of the battery module of Example F-1.The curve of solid line having symbol (2) shows a discharge curve of thebattery module of Example F-2. The curve of broken line having symbol(3) shows a discharge curve of the battery module of Example F-3. Inaddition, the curve of solid line having symbol (4) shows a dischargecurve of the battery module of Example F-4.

From the results shown in FIG. 14, it is found that when the products ofExamples A-4, A-5, A-6 and A-9 are used as the negative electrode activematerial, the battery modules having an average operating-voltage withina range of about 12.5 V to 13.5 V can be produced. It also is found thateach discharge curve has a different voltage gradient. As describedabove, the operating voltage of the battery module can be designedaccording to the use by changing the average operating-voltage or thevoltage gradient. For example, when a motor assist type hybrid car or anidling stop system is constructed by combining each battery module witha 12 V lead storage battery for automobiles, it is possible to design abattery pack voltage capable of preventing over-discharge of a leadstorage battery upon a high load or adapting a voltage fluctuation uponan input of a regenerative energy.

The nonaqueous electrolyte battery using spinel lithium titanate(Li₄Ti₅O₁₂) as the negative electrode has a lowaverage-operating-voltage, and thus it is necessary to connect sixbatteries in series, in order to obtain a voltage compatible with a leadstorage battery for automobiles. On the other hand, as explainedreferring to examples, when the products of Example A-series, ExampleB-series, Example C-series and Example D-series are used as the negativeelectrode, the average operating-voltage of the nonaqueous electrolytebattery can be increased. When the products of Example A-series, ExampleB-series, Example C-series and Example D-series are used, accordingly,even if the number of the nonaqueous electrolyte batteries connected inseries is changed to five, a battery module capable of exhibiting avoltage compatible with the 12 V lead storage battery for automobilescan be constructed, and thus a battery pack capable of exhibiting avoltage compatible with the 12 V lead storage battery for automobilescan be also constructed. The products of Example A-series, ExampleB-series, Example C-series, and Example D-series, accordingly, canrealize a small size battery pack capable of exhibiting a low resistanceand a high energy density at a low cost.

As explained above, according to at least one of the embodiments andExamples, the active material containing the composite oxide having theorthorhombic crystal structure is provided. The composite oxide isrepresented by the general formulaLi_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O_(14+δ). The composite oxide canshow a large potential change with a change of the capacity in apotential range of 1.0 V (vs. to 1.45 V (vs. Li/Li⁺). The average actionpotential of the composite oxide can be controlled by changing the Naamount. In addition, the composite oxide can have a crystal structure inwhich lithium ions are easily inserted into and extracted from thecrystal structure, and thus a high reversible capacity at the charge anddischarge and excellent life span property can be realized. As a result,the active material can realize a nonaqueous electrolyte battery capableof showing high energy density, high battery voltage, and excellent lifespan property, and easily controlling the voltage.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. An active material comprising: a composite oxidehaving an orthorhombic crystal structure and represented by a generalformula of Li_(2+w)Na_(2−x)M1_(y)Ti_(6−z)M2_(z)O_(14+δ), wherein the M1is at least one selected from the group consisting of Cs and K, the M2is at least one selected from the group consisting of Zr, Sn, V, Nb, Ta,Mo, W, Fe, Co, Mn, and Al, and w is within a range of 0≦w≦4, x is withina range of 0<x<2, y is within a range of 0≦y<2, z is within a range of0<z≦6, and δ is within a range of −0.5≦δ≦0.5.
 2. The active materialaccording to claim 1, wherein the M2 is at least one selected from thegroup consisting of trivalent Fe, Co, Mn and Al, tetravalent Zr and Sn,pentavalent V, Nb and Ta, and hexavalent Mo and W.
 3. The activematerial according to claim 1, wherein, in an X-ray diffraction diagramfor the composite oxide obtained by a powder X-ray diffraction methodusing Cu—Kα rays, an intensity ratio I_(L)/I_(H) is within a range of2.25≦I_(L)/I_(H)≦3.5, wherein the intensity I_(L) is an intensity of astrongest diffraction peak appearing in a range of 17°≦2θ≦18.5°, and theintensity I_(H) is an intensity of a strongest diffraction peakappearing in a range of 18.5°≦2θ≦19.5°.
 4. The active material accordingto claim 1, wherein the orthorhombic crystal structure belongs to aspace group Fmmm, and in an X-ray diffraction diagram for the compositeoxide obtained by a powder X-ray diffraction method using Cu—Kα rays, anintensity ratio is within a range of 2.25≦I_(L1)/I_(H1)≦3.5, wherein theintensity I_(L1) is an intensity of a diffraction peak corresponding toa (111) plane, and the intensity I_(H1) is an intensity of a diffractionpeak corresponding to a (202) plane.
 5. The active material according toclaim 1, wherein, the composite oxide is represented by a generalformula of Li_(2+w)Na_(2−x)Ti_(6−z)M2_(z)O_(14+δ), the M2 is at leastone selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Fe,Co, Mn, and Al, and w is within a range of 0≦w≦4, x is within a range of0<x<2, z is within a range of 0<z≦6, and δ is within a range of−0.5≦δ≦0.5.
 6. The active material according to claim 1, the M2comprises Nb.
 7. The active material according to claim 1, the M2comprises two or more elements which have different valences.
 8. Theactive material according to claim 1, wherein the composite oxide is aparticle, the active material further comprises a layer covering atleast a part of a surface of the particle of the composite oxide, andthe layer comprises carbon and/or lithium titanate.
 9. The activematerial according to claim 1, wherein the active material is an activematerial for a battery.
 10. A nonaqueous electrolyte battery comprising:a negative electrode comprising the active material according to claim1; a positive electrode; and a nonaqueous electrolyte.
 11. Thenonaqueous electrolyte battery according to claim 10, wherein thenegative electrode comprises a current collector and a negativeelectrode layer formed on the current collector, the negative electrodelayer comprises the active material, a density of the negative electrodelayer is in a range of 1.8 g/cm³ to 2.8 g/cm³.
 12. A battery packcomprising the nonaqueous electrolyte battery according to claim
 10. 13.A battery pack comprising nonaqueous electrolyte batteries, each ofwhich comprises: a negative electrode comprising the active materialaccording to claim 1; a positive electrode; and a nonaqueouselectrolyte, wherein the nonaqueous electrolyte batteries areelectrically connected in series and/or in parallel.
 14. A batterymodule comprises nonaqueous electrolyte batteries, each of whichcomprises: a negative electrode comprising the active material accordingto claim 1; a positive electrode; and a nonaqueous electrolyte, andwherein the nonaqueous electrolyte batteries are electrically connectedin series.